Systems and methods for stage-based control related to TRIAC dimmers

ABSTRACT

System controller and method for a lighting system according to certain embodiments. For example, the system controller includes a first controller terminal configured to receive a first signal, and a second controller terminal coupled to a first transistor terminal of a transistor. The transistor further includes a second transistor terminal and a third transistor terminal. The second transistor terminal is coupled to a first winding terminal of a winding, and the winding further includes a second winding terminal coupled to a capacitor. Additionally, the system controller includes a third controller terminal coupled to the third transistor terminal of the transistor, and a fourth controller terminal coupled to a resistor and configured to receive a second signal. The second signal represents a magnitude of a current flowing through at least the winding, the third controller terminal, the fourth controller terminal, and the resistor.

1. CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/385,327, filed Apr. 16, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/849,452, filed Dec. 20, 2017, which claimspriority to Chinese Patent Application No. 201711235958.9, filed Nov.30, 2017, all of the above-referenced applications being incorporated byreference herein for all purposes.

Additionally, this application is related to U.S. patent applicationSer. Nos. 15/364,100, 14/593,734 and 14/451,656, all of which areincorporated by reference herein for all purposes.

2. BACKGROUND OF THE INVENTION

Certain embodiments of the present invention are directed to integratedcircuits. More particularly, some embodiments of the invention provide asystem and method for stage-based control related to TRIAC dimmer.Merely by way of example, some embodiments of the invention have beenapplied to driving one or more light emitting diodes (LEDs). But itwould be recognized that the invention has a much broader range ofapplicability.

A conventional lighting system may include or may not include a TRIACdimmer that is a dimmer including a Triode for Alternating Current(TRIAC). For example, the TRIAC dimmer is either a leading-edge TRIACdimmer or a trailing-edge TRIAC dimmer. Often, the leading-edge TRIACdimmer and the trailing-edge TRIAC dimmer are configured to receive analternating-current (AC) input voltage, process the AC input voltage byclipping part of the waveform of the AC input voltage, and generate avoltage that is then received by a rectifier (e.g., a full waverectifying bridge) in order to generate a rectified output voltage.

FIG. 1 shows certain conventional timing diagrams for a leading-edgeTRIAC dimmer and a trailing-edge TRIAC dimmer. The waveforms 110, 120,and 130 are merely examples. Each of the waveforms 110, 120, and 130represents a rectified output voltage as a function of time that isgenerated by a rectifier. For the waveform 110, the rectifier receivesan AC input voltage without any processing by a TRIAC dimmer. For thewaveform 120, an AC input voltage is received by a leading-edge TRIACdimmer, and the voltage generated by the leading-edge TRIAC dimmer isreceived by the rectifier, which then generates the rectified outputvoltage. For the waveform 130, an AC input voltage is received by atrailing-edge TRIAC dimmer, and the voltage generated by thetrailing-edge TRIAC dimmer is received by the rectifier, which thengenerates the rectified output voltage.

As shown by the waveform 110, each cycle of the rectified output voltagehas, for example, a phase angel (e.g., ϕ) that changes from 0° to 180°and then from 180° to 360°. As shown by the waveform 120, theleading-edge TRIAC dimmer usually processes the AC input voltage byclipping part of the waveform that corresponds to the phase angelstarting at 0° or starting at 180°. As shown by the waveform 130, thetrailing-edge TRIAC dimmer often processes the AC input voltage byclipping part of the waveform that corresponds to the phase angel endingat 180° or ending at 360°.

Various conventional technologies have been used to detect whether ornot a TRIAC dimmer has been included in a lighting system, and if aTRIAC dimmer is detected to be included in the lighting system, whetherthe TRIAC dimmer is a leading-edge TRIAC dimmer or a trailing-edge TRIACdimmer. In one conventional technology, a rectified output voltagegenerated by a rectifier is compared with a threshold voltage V_(th_on)in order to determine a turn-on time period T_(on). If the turn-on timeperiod T_(on) is approximately equal to the duration of a half cycle ofthe AC input voltage, no TRIAC dimmer is determined to be included inthe lighting system; if the turn-on time period T_(on) is notapproximately equal to but is smaller than the duration of a half cycleof the AC input voltage, a TRIAC dimmer is determined to be included inthe lighting system. If a TRIAC dimmer is determined to be included inthe lighting system, a turn-on voltage slope V_(on_slope) is comparedwith the threshold voltage slope V_(th_slope). If the turn-on voltageslope V_(on_slope) is larger than the threshold voltage slopeV_(th_slope), the TRIAC dimmer is determined to be a leading-edge TRIACdimmer; if the turn-on voltage slope V_(on_slope) is smaller than thethreshold voltage slope V_(th_slope), the TRIAC dimmer is determined tobe a trailing-edge TRIAC dimmer.

If a conventional lighting system includes a TRIAC dimmer and lightemitting diodes (LEDs), the light emitting diodes may flicker if thecurrent that flows through the TRIAC dimmer falls below a holdingcurrent that is, for example, required by the TRIAC dimmer. As anexample, if the current that flows through the TRIAC dimmer falls belowthe holding current, the TRIAC dimmer may turn on and off repeatedly,thus causing the LEDs to flicker. As another example, the various TRIACdimmers made by different manufacturers have different holding currentsranging from 5 mA to 50 mA.

The light emitting diodes (LEDs) are gradually replacing incandescentlamps and becoming major lighting sources. The LEDs can provide highenergy efficiency and long lifetime. The dimming control of LEDs,however, faces significant challenges because of insufficient dimmercompatibility. For certain historical reasons, the TRIAC dimmers oftenare designed primarily suitable for incandescent lamps, which usuallyinclude resistive loads with low lighting efficiency. Such low lightingefficiency of the resistive loads often helps to satisfy theholding-current requirements of TRIAC dimmers. Hence the TRIAC dimmersmay work well with the incandescent lamps. In contrast, for highlyefficient LEDs, the holding-current requirements of TRIAC dimmersusually are difficult to meet. The LEDs often need less amount of inputpower than the incandescent lamps for the same level of illumination.

In order to meet the holding-current requirements of the TRIAC dimmers,some conventional techniques use a bleeder for a lighting system. FIG. 2is a simplified diagram of a conventional lighting system that includesa bleeder. As shown, the conventional lighting system 200 includes aTRIAC dimmer 210, a rectifier 220, a bleeder 224, a diode 226,capacitors 230, 232, 234, 236 and 238, a pulse-width-modulation (PWM)controller 240, a winding 260, a transistor 262, resistors 270, 272,274, 276, 278 and 279, and one or more LEDs 250. The PWM controller 240includes controller terminals 242, 244, 246, 248, 252, 254, 256 and 258.For example, the PWM controller 240 is a chip, and each of thecontroller terminals 242, 244, 246, 248, 252, 254, 256 and 258 is a pin.In yet another example, the winding 260 includes winding terminals 263and 265.

The TRIAC dimmer 210 receives an AC input voltage 214 (e.g., VAC) andgenerates a voltage 212. The voltage 212 is received by the rectifier220 (e.g., a full wave rectifying bridge), which then generates arectified output voltage 222. The rectified output voltage 222 is largerthan or equal to zero. The resistor 279 includes resistor terminals 235and 239, and the capacitor 236 includes capacitor terminals 281 and 283.The resistor terminal 235 receives the rectified output voltage 222. Theresistor terminal 239 is connected to the capacitor terminal 281, thecontroller terminal 252, and a gate terminal of the transistor 262. Thegate terminal of the transistor 262 receives a gate voltage 237 from theresistor terminal 239, the capacitor terminal 281, and the controllerterminal 252. The capacitor terminal 283 receives a ground voltage.

As shown in FIG. 2, the rectified output voltage 222 is used to chargethe capacitor 236 through the resistor 279 to raise the gate voltage237. In response, if the result of the gate voltage 237 minus a sourcevoltage at a source terminal of the transistor 262 reaches or exceeds atransistor threshold voltage, the transistor 262 is turned on. When thetransistor 262 is turned on, through the transistor 262 and thecontroller terminal 254, a current flows into the PWM controller 240 anduses an internal path to charge the capacitor 232. In response, thecapacitor 232 generates a capacitor voltage 233, which is received bythe controller terminal 244. If the capacitor voltage 233 reaches orexceeds an undervoltage-lockout threshold of the PWM controller 240, thePWM controller 240 starts up.

After the PWM controller 240 has started up, a pulse-width-modulation(PWM) signal 255 is generated. The PWM signal 255 has a signal frequencyand a duty cycle. The PWM signal 255 is received by the source terminalof the transistor 262 through the terminal 254. The transistor 262 isturned on and off, in order to make an output current 266 constant andprovide the output current 266 to the one or more LEDs 250, by workingwith at least the capacitor 238.

As shown in FIG. 2, a drain voltage at a drain terminal of thetransistor 262 is received by a voltage divider that includes theresistors 276 and 278. The drain terminal of the transistor 262 isconnected to the winding terminal 265 of the winding 260, and thewinding terminal 263 of the winding 260 is connected to the capacitor230 and the resistor 279. In response, the voltage divider generates avoltage 277, which is received by the controller terminal 256. The PWMcontroller 240 uses the voltage 277 to detect the end of ademagnetization process of the winding 260. The detection of the end ofthe demagnetization process is used to control an internal erroramplifier of the PWM controller 240, and through the controller terminal246, to control charging and discharging of the capacitor 234.

Also, after the PWM controller 240 has started up, the resistor 274 isused to detect a current 261, which flows through the winding 260. Thecurrent 261 flows from the winding 260 through the resistor 274, whichin response generates a sensing voltage 275. The sensing voltage 275 isreceived by the PWM controller 240 at the controller terminal 258, andis processed by the PWM controller 240 on a cycle-by-cycle basis. Thepeak magnitude of the sensing voltage 275 is sampled, and the sampledsignal is sent to an input terminal of the internal error amplifier ofthe PWM controller 240. The other input terminal of the internal erroramplifier receives a reference voltage V_(ref).

As shown in FIG. 2, the rectified output voltage 222 is received by avoltage divider that includes the resistors 270 and 272. In response,the voltage divider generates a voltage 271, which is received by thecontroller terminal 242. The PWM controller 240 processes the voltage271 and determines phase angle of the voltage 271. Based on the detectedrange of phase angle of the voltage 271, the PWM controller 240 adjuststhe reference voltage V_(ref), which is received by the internal erroramplifier.

The bleeder 224 is used to ensure that, when the TRIAC dimmer 210 isfired on, an input current 264 that flows through the TRIAC dimmer 210is larger than a holding current required by the TRIAC dimmer 210, inorder to avoid misfire of the TRIAC dimmer 210 and also avoid flickeringof the one or more LEDs 250. For example, the bleeder 224 includes aresistor, which receives the rectified output voltage 222 at oneresistor terminal of the resistor and receives the ground voltage at theother resistor terminal of the resistor. The resistor of the bleeder 224allows a bleeder current 268 to flow through as at least part of theinput current 264. In another example, if the holding current requiredby the TRIAC dimmer 210 is small and if the average current that flowsthrough the transistor 262 can satisfy the holding current requirementof the TRIAC dimmer 210, the bleeder 224 is not activated or is simplyremoved.

As shown in FIG. 2, the lighting system 200 includes, for example, aquasi-resonant system with a buck-boost topology. The output current 266of the quasi-resonant system is received by the one or more LEDs 250 andis determined as follows:

$\begin{matrix}{I_{o} = {\frac{1}{2} \times \frac{V_{ref}}{R_{cs}}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$where I_(o) represents the output current 266 of the quasi-resonantsystem of the lighting system 200. Additionally, V_(ref) represents thereference voltage received by the internal error amplifier of the PWMcontroller 240. Moreover, R_(cs) represents the resistance of theresistor 274.

FIG. 3 is a simplified diagram showing certain conventional componentsof the lighting system 200 as shown in FIG. 2. Thepulse-width-modulation (PWM) controller 240 includes a dimming controlcomponent 300 and a transistor 350. The dimming control component 300includes a phase detector 310, a reference voltage generator 320, apulse-width-modulation (PWM) signal generator 330, and a driver 340.

FIG. 4 shows certain conventional timing diagrams for the lightingsystem 200 as shown in FIGS. 2 and 3. The waveform 471 represents thevoltage 271 as a function of time, the waveform 412 represents the phasesignal 312 as a function of time, the waveform 475 represents thesensing voltage 275 as a function of time, and the waveform 464represents cycle-by-cycle average of the input current 264 as a functionof time.

As shown by FIGS. 3 and 4, the lighting system 200 uses a closed loop toperform dimming control. The phase detector 310 receives the voltage 271through the terminal 242, detects phase angle of the voltage 271, andgenerates a phase signal 312 that indicates the detected range of phaseangle of the voltage 271. As shown by the waveform 471, the voltage 271becomes larger than a dim-on threshold voltage (e.g., V_(th_dimon)) attime t_(a) and becomes smaller than a dim-off threshold voltage (e.g.,V_(th_dimoff)) at time t_(b). The dim-on threshold voltage (e.g.,V_(th_dimon)) is equal to or different from the dim-off thresholdvoltage (e.g., V_(th_dimoff)). The time duration from time t_(a) to timet_(b) is represented by T_(R), during which the phase signal 312 is atthe logic high level, as shown by the waveform 412. The time durationT_(R) represents the detected range of phase angle of the voltage 271.

During the time duration T_(R), the sensing voltage 275 ramps up anddown. For example, during the time duration T_(R), within a switchingperiod (e.g., T_(SW)), the sensing voltage 275 ramps up, ramps down, andthen remains constant (e.g., remains equal to zero) until the end of theswitching period (e.g., until the end of T_(SW)).

The phase signal 312 is received by the reference voltage generator 320,which uses the detected range of phase angle of the voltage 271 togenerate the reference voltage 322 (e.g., V_(ref)). As shown in FIG. 3,the reference voltage 322 (e.g., V_(ref)) is received by the PWM signalgenerator 330. For example, the PWM signal generator 330 includes theinternal error amplifier of the PWM controller 240. In another example,the PWM signal generator 330 also receives the sensing voltage 275 andgenerates a pulse-width-modulation (PWM) signal 332. The PWM signal 332is received by the driver 340, which in response generates a drivesignal 342 and outputs the drive signal 342 to the transistor 350. Thetransistor 350 includes a gate terminal, a drain terminal, and a sourceterminal. The gate terminal of the transistor 350 receives the drivesignal 342. The drain terminal of the transistor 350 is coupled to thecontroller terminal 254, and the source terminal of the transistor 350is coupled to the controller terminal 258.

As shown by the waveform 475, the reference voltage 322 (e.g., V_(ref))is used by the PWM signal generator 330 to generate the PWM signal 332,which is then used to control the peak magnitude (e.g., CS_peak) of thesensing voltage 275 for each PWM cycle during the time duration T_(R).For example, each PWM cycle corresponds to a time duration that is equalto the switching period (e.g., T_(SW)) in magnitude. In another example,if the detected range of phase angle of the voltage 271 (e.g.,corresponding to T_(R)) becomes larger, the reference voltage 322 (e.g.,V_(ref)) also becomes larger. In yet another example, if the detectedrange of phase angle of the voltage 271 (e.g., corresponding to T_(R))becomes smaller, the reference voltage 322 (e.g., V_(ref)) also becomessmaller.

According to Equation 1, if the reference voltage 322 (e.g., V_(ref))becomes larger, the output current 266 (e.g., I_(o)) of thequasi-resonant system of the lighting system 200 also becomes larger; ifthe reference voltage 322 (e.g., V_(ref)) becomes smaller, the outputcurrent 266 (e.g., I_(o)) of the quasi-resonant system of the lightingsystem 200 also becomes smaller.

As shown by FIG. 2, the cycle-by-cycle average of the input current 264is approximately equal to the sum of cycle-by-cycle average of theoutput current 266 (e.g., I_(o)) and the bleeder current 268. During thetime duration T_(R), within each switching cycle of the PWM signal 332,the output current 266 changes with time, so the average of the outputcurrent 266 within each switching cycle is used to determine thecycle-by-cycle average (e.g., I_PWM_av) of the output current 266 as afunction of time. When the time duration T_(R) becomes smaller, thereference voltage 322 (e.g., V_(ref)) also becomes smaller and the oneor more LEDs 250 are expected to become dimmer. When the time durationT_(R) becomes too small, the reference voltage 322 (e.g., V_(ref)) alsobecomes too small and the cycle-by-cycle average (e.g., I_PWM_av) of theoutput current 266 during the time duration T_(R) becomes smaller thanthe holding current (e.g., I_holding) required by the TRIAC dimmer 210.In order to avoid misfire of the TRIAC dimmer 210 and also avoidflickering of the one or more LEDs 250, the bleeder current 268 (e.g.,I_bleed) is provided in order to increase the cycle-by-cycle average ofthe input current 264 during the time duration T_(R). As shown by thewaveform 464, the cycle-by-cycle average of the input current 264 duringthe time duration T_(R) becomes larger than the holding current requiredby the TRIAC dimmer 210.

As shown in FIG. 3, the driver 340 outputs the drive signal 342 to thetransistor 350. The transistor 350 is turned on if the drive signal 342is at a logic high level, and the transistor 350 is turned off if thedrive signal 342 is at a logic low level. When the transistor 262 andthe transistor 350 are turned on, the current 261 flows through thewinding 260, the transistor 262, the controller terminal 254, thetransistor 350, the controller terminal 258, and the resistor 274. Ifthe transistor 350 becomes turned off when the transistor 262 is stillturned on, the transistor 262 then also becomes turned off and thewinding 260 starts to discharge. If the transistor 350 becomes turned onwhen the transistor 262 is still turned off, the transistor 262 thenalso becomes turned on and the winding 260 starts to charge.

As shown in FIGS. 2-4, the lighting system 200 uses a closed loop toperform dimming control. For example, the lighting system 200 detectsthe range of phase angle of the voltage 271, and based on the detectedrange of phase angle, adjusts the reference voltage V_(ref) that isreceived by the internal error amplifier of the PWM controller 240. Inanother example, the lighting system 200 provides energy to the one ormore LEDs 250 throughout the entire time period of each switching cycleduring the time duration T_(R), which corresponds to the unclipped partof the waveform of the AC input voltage 214 (e.g., VAC).

As discussed above, a bleeder (e.g., the bleeder 224) can help alighting system (e.g., the lighting system 200) to meet theholding-current requirement of a TRIAC dimmer (e.g., the TRIAC dimmer210) in order to avoid misfire of the TRIAC dimmer (e.g., the TRIACdimmer 210) and avoid flickering of one or more LEDs (e.g., the one ormore LEDs 250). But the bleeder (e.g., the bleeder 224) usuallyincreases heat generation and reduces energy efficiency of the lightingsystem (e.g., the lighting system 200). Such reduction in energyefficiency usually becomes more severe if a bleeder current (e.g., thebleeder current 268) becomes larger. This reduced energy efficiencyoften prevents the lighting system (e.g., the lighting system 200) fromtaking full advantage of high energy efficiency and long lifetime of theone or more LEDs (e.g., the one or more LEDs 250).

Hence it is highly desirable to improve the techniques of dimmingcontrol.

3. BRIEF SUMMARY OF THE INVENTION

Certain embodiments of the present invention are directed to integratedcircuits. More particularly, some embodiments of the invention provide asystem and method for stage-based control related to TRIAC dimmer.Merely by way of example, some embodiments of the invention have beenapplied to driving one or more light emitting diodes (LEDs). But itwould be recognized that the invention has a much broader range ofapplicability.

According to one embodiment, a system controller for a lighting systemincludes a first controller terminal configured to receive a firstsignal, and a second controller terminal coupled to a first transistorterminal of a transistor. The transistor further includes a secondtransistor terminal and a third transistor terminal. The secondtransistor terminal is coupled to a first winding terminal of a winding,and the winding further includes a second winding terminal coupled to acapacitor. Additionally, the system controller includes a thirdcontroller terminal coupled to the third transistor terminal of thetransistor, and a fourth controller terminal coupled to a resistor andconfigured to receive a second signal. The second signal represents amagnitude of a current flowing through at least the winding, the thirdcontroller terminal, the fourth controller terminal, and the resistor.The system controller is configured to: in response to the first signalbecoming larger than a first threshold in magnitude at a first time,cause the second signal to ramp up and down during a first duration oftime; and in response to the first signal becoming smaller than a secondthreshold in magnitude at a third time, cause the second signal to rampup and down during a second duration of time. The first duration of timestarts at the first time and ends at a second time. The second durationof time starts at the third time and ends at a fourth time. The systemcontroller is further configured to cause the second signal to remainequal to a constant magnitude from the second time to the third time.The first time is earlier than the second time, the second time isearlier than the third time, and the third time is earlier than thefourth time.

According to another embodiment, a system controller for a lightingsystem includes a first controller terminal configured to receive afirst signal, and a second controller terminal coupled to a firsttransistor terminal of a transistor. The transistor further includes asecond transistor terminal and a third transistor terminal, and thesecond transistor terminal is coupled to a winding. Additionally, thesystem controller further includes a third controller terminal coupledto the third transistor terminal of the transistor, and a fourthcontroller terminal coupled to a resistor and configured to receive asecond signal. The second signal represents a magnitude of a currentflowing through at least the winding, the third controller terminal, thefourth controller terminal, and the resistor. The system controller isconfigured to: in response to the first signal becoming larger than afirst threshold in magnitude at a first time, cause the second signal toramp up and down during a duration of time. The duration of time startsat a second time and ends at a third time. The third time is a time whenthe first signal becomes smaller than a second threshold in magnitude.The system controller is further configured to cause the second signalto remain equal to a constant magnitude from the first time to thesecond time. The first time is earlier than the second time, and thesecond time is earlier than the third time.

According to yet another embodiment, a system controller for a lightingsystem includes a first controller terminal configured to receive afirst signal. The first signal is related to a dimming-control phaseangle. Additionally, the system controller includes a second controllerterminal coupled to a first transistor terminal of a transistor. Thetransistor further includes a second transistor terminal and a thirdtransistor terminal, and the second transistor terminal is coupled to awinding. Moreover, the system controller includes a third controllerterminal coupled to the third transistor terminal of the transistor, anda fourth controller terminal coupled to a resistor and configured toreceive a second signal. The second signal represents a magnitude of acurrent flowing through at least the winding, the third controllerterminal, the fourth controller terminal, and the resistor. The systemcontroller is configured to, in response to the first signal satisfyingone or more predetermined conditions: cause the second signal to ramp upand down during a first duration of time; and cause the second signal toramp up and down during a second duration of time. The first duration oftime starts at a first time and ends at a second time, and the secondtime is the same as or later than the first time. The second duration oftime starts at a third time and ends at a fourth time, and the fourthtime is the same as or later than the third time. The system controlleris further configured to: in response to the dimming-control phase angleincreasing from a first angle magnitude to a second angle magnitude,keep the first duration of time at a first predetermined constant; inresponse to the dimming-control phase angle increasing from the secondangle magnitude to a third angle magnitude, increase the first durationof time; and in response to the dimming-control phase angle increasingfrom the third angle magnitude to a fourth angle magnitude, keep thefirst duration of time at a second predetermined constant.

According to yet another embodiment, a system controller for a lightingsystem includes a first controller terminal configured to receive afirst signal. The first signal is related to a dimming-control phaseangle. Additionally, the system controller includes a second controllerterminal coupled to a first transistor terminal of a transistor. Thetransistor further includes a second transistor terminal and a thirdtransistor terminal, and the second transistor terminal is coupled to awinding. Moreover, the system controller includes a third controllerterminal coupled to the third transistor terminal of the transistor, anda fourth controller terminal coupled to a resistor and configured toreceive a second signal. The second signal represents a magnitude of acurrent flowing through at least the winding, the third controllerterminal, the fourth controller terminal, and the resistor. The systemcontroller is configured to, in response to the first signal satisfyingone or more predetermined conditions: cause the second signal to ramp upand down during a first duration of time; and cause the second signal toramp up and down during a second duration of time. The first duration oftime starts at a first time and ends at a second time, and the secondtime is the same as or later than the first time. The second duration oftime starts at a third time and ends at a fourth time, and the fourthtime is the same as or later than the third time. The system controlleris further configured to: in response to the dimming-control phase angleincreasing from a first angle magnitude to a second angle magnitude,keep the second duration of time at a first predetermined constant; inresponse to the dimming-control phase angle increasing from the secondangle magnitude to a third angle magnitude, increase the second durationof time; and in response to the dimming-control phase angle increasingfrom the third angle magnitude to a fourth angle magnitude, keep thesecond duration of time at a second predetermined constant.

According to yet another embodiment, a system controller for a lightingsystem includes a first controller terminal configured to receive afirst signal. The first signal is related to a dimming-control phaseangle. Additionally, the system controller includes a second controllerterminal coupled to a first transistor terminal of a transistor. Thetransistor further includes a second transistor terminal and a thirdtransistor terminal, and the second transistor terminal is coupled to awinding. Moreover, the system controller includes a third controllerterminal coupled to the third transistor terminal of the transistor, anda fourth controller terminal coupled to a resistor and configured toreceive a second signal. The second signal represents a magnitude of acurrent flowing through at least the winding, the third controllerterminal, the fourth controller terminal, and the resistor. The systemcontroller is configured to, in response to the first signal satisfyingone or more predetermined conditions: cause the second signal to ramp upand down during a first duration of time; and cause the second signal toramp up and down during a second duration of time. The first duration oftime starts at a first time and ends at a second time, and the secondtime is the same as or later than the first time. The second duration oftime starts at a third time and ends at a fourth time, and the fourthtime is the same as or later than the third time. The sum of the firstduration of time and the second duration of time is equal to a totalduration of time. The system controller is further configured to: inresponse to the dimming-control phase angle increasing from a firstangle magnitude to a second angle magnitude, keep the total duration oftime at a first predetermined constant; in response to thedimming-control phase angle increasing from the second angle magnitudeto a third angle magnitude, increase the total duration of time; and inresponse to the dimming-control phase angle increasing from the thirdangle magnitude to a fourth angle magnitude, keep the total duration oftime at a second predetermined constant.

According to yet another embodiment, a system controller for a lightingsystem includes a first controller terminal configured to receive afirst signal, and a second controller terminal coupled to a firsttransistor terminal of a transistor. The transistor further includes asecond transistor terminal and a third transistor terminal, and thesecond transistor terminal is coupled to a first winding terminal of awinding. The winding further includes a second winding terminal coupledto a capacitor. Additionally, the system controller includes a thirdcontroller terminal coupled to the third transistor terminal of thetransistor, and a fourth controller terminal coupled to a resistor andconfigured to receive a second signal. The second signal represents amagnitude of a current flowing through at least the winding, the thirdcontroller terminal, the fourth controller terminal, and the resistor.The system controller is configured to determine whether or not a TRIACdimmer is detected to be included in the lighting system and if theTRIAC dimmer is detected to be included in the lighting system, whetherthe TRIAC dimmer is a leading-edge TRIAC dimmer or a trailing-edge TRIACdimmer. The system controller is further configured to, if the TRIACdimmer is detected to be included in the lighting system and the TRIACdimmer is the leading-edge TRIAC dimmer: in response to the first signalbecoming larger than a first threshold in magnitude at a first time,cause the second signal to ramp up and down during a first duration oftime; and in response to the first signal becoming smaller than a secondthreshold in magnitude at a third time, cause the second signal to rampup and down during a second duration of time. The first duration of timestarts at the first time and ends at a second time, and the secondduration of time starts at the third time and ends at a fourth time. Thesystem controller is further configured to, if the TRIAC dimmer isdetected to be included in the lighting system and the TRIAC dimmer isthe trailing-edge TRIAC dimmer: in response to the first signal becominglarger than the first threshold in magnitude at a fifth time, cause thesecond signal to ramp up and down during a duration of time. Theduration of time starts at a sixth time and ends at a seventh time. Theseventh time is a time when the first signal becomes smaller than thesecond threshold in magnitude.

According to yet another embodiment, a method for a lighting systemincludes receiving a first signal, and receiving a second signal. Thesecond signal represents a magnitude of a current flowing through atleast a winding. Additionally, the method includes: in response to thefirst signal becoming larger than a first threshold in magnitude at afirst time, causing the second signal to ramp up and down during a firstduration of time; and in response to the first signal becoming smallerthan a second threshold in magnitude at a third time, causing the secondsignal to ramp up and down during a second duration of time. The firstduration of time starts at the first time and ends at a second time, andthe second duration of time starts at the third time and ends at afourth time. Moreover, the method includes causing the second signal toremain equal to a constant magnitude from the second time to the thirdtime. The first time is earlier than the second time, the second time isearlier than the third time, and the third time is earlier than thefourth time.

According to yet another embodiment, a method for a lighting systemincludes receiving a first signal and receiving a second signal. Thesecond signal represents a magnitude of a current flowing through atleast a winding. Additionally, the method includes: in response to thefirst signal becoming larger than a first threshold in magnitude at afirst time, causing the second signal to ramp up and down during aduration of time. The duration of time starts at a second time and endsat a third time, and the third time is a time when the first signalbecomes smaller than a second threshold in magnitude. Moreover, themethod includes causing the second signal to remain equal to a constantmagnitude from the first time to the second time. The first time isearlier than the second time, and the second time is earlier than thethird time.

According to yet another embodiment, a method for a lighting systemincludes receiving a first signal. The first signal is related to adimming-control phase angle. Additionally, the method includes receivinga second signal. The second signal represents a magnitude of a currentflowing through at least a winding. Moreover, the method includes, inresponse to the first signal satisfying one or more predeterminedconditions: causing the second signal to ramp up and down during a firstduration of time; and causing the second signal to ramp up and downduring a second duration of time. The first duration of time starts at afirst time and ends at a second time, and the second time is the same asor later than the first time. The second duration of time starts at athird time and ends at a fourth time, and the fourth time is the same asor later than the third time. The causing the second signal to ramp upand down during a first duration of time includes: in response to thedimming-control phase angle increasing from a first angle magnitude to asecond angle magnitude, keeping the first duration of time at a firstpredetermined constant; in response to the dimming-control phase angleincreasing from the second angle magnitude to a third angle magnitude,increasing the first duration of time; and in response to thedimming-control phase angle increasing from the third angle magnitude toa fourth angle magnitude, keeping the first duration of time at a secondpredetermined constant.

According to yet another embodiment, a method for a lighting systemincludes receiving a first signal. The first signal is related to adimming-control phase angle. Additionally, the method includes receivinga second signal. The second signal represents a magnitude of a currentflowing through at least a winding. Moreover, the method includes, inresponse to the first signal satisfying one or more predeterminedconditions: causing the second signal to ramp up and down during a firstduration of time; and causing the second signal to ramp up and downduring a second duration of time. The first duration of time starts at afirst time and ends at a second time, and the second time is the same asor later than the first time. The second duration of time starts at athird time and ends at a fourth time, and the fourth time is the same asor later than the third time. The causing the second signal to ramp upand down during a second duration of time includes: in response to thedimming-control phase angle increasing from a first angle magnitude to asecond angle magnitude, keeping the second duration of time at a firstpredetermined constant; in response to the dimming-control phase angleincreasing from the second angle magnitude to a third angle magnitude,increasing the second duration of time; and in response to thedimming-control phase angle increasing from the third angle magnitude toa fourth angle magnitude, keeping the second duration of time at asecond predetermined constant.

According to yet another embodiment, a method for a lighting systemincludes receiving a first signal. The first signal is related to adimming-control phase angle. Additionally, the method includes receivinga second signal. The second signal represents a magnitude of a currentflowing through at least a winding. Moreover, the method includes, inresponse to the first signal satisfying one or more predeterminedconditions: causing the second signal to ramp up and down during a firstduration of time; and causing the second signal to ramp up and downduring a second duration of time. The first duration of time starts at afirst time and ends at a second time, and the second time is the same asor later than the first time. The second duration of time starts at athird time and ends at a fourth time, and the fourth time is the same asor later than the third time. A sum of the first duration of time andthe second duration of time is equal to a total duration of time. Thecausing the second signal to ramp up and down during a first duration oftime and the causing the second signal to ramp up and down during asecond duration of time include: in response to the dimming-controlphase angle increasing from a first angle magnitude to a second anglemagnitude, keeping the total duration of time at a first predeterminedconstant; in response to the dimming-control phase angle increasing fromthe second angle magnitude to a third angle magnitude, increasing thetotal duration of time; and in response to the dimming-control phaseangle increasing from the third angle magnitude to a fourth anglemagnitude, keeping the total duration of time at a second predeterminedconstant.

According to yet another embodiment, a method for a lighting systemincludes receiving a first signal and receiving a second signal. Thesecond signal represents a magnitude of a current flowing through atleast a winding. Additionally, the method includes determining whetheror not a TRIAC dimmer is detected to be included in the lighting systemand if the TRIAC dimmer is detected to be included in the lightingsystem, whether the TRIAC dimmer is a leading-edge TRIAC dimmer or atrailing-edge TRIAC dimmer. Moreover, the method includes, if the TRIACdimmer is detected to be included in the lighting system and the TRIACdimmer is the leading-edge TRIAC dimmer: in response to the first signalbecoming larger than a first threshold in magnitude at a first time,causing the second signal to ramp up and down during a first duration oftime; and in response to the first signal becoming smaller than a secondthreshold in magnitude at a third time, causing the second signal toramp up and down during a second duration of time. The first duration oftime starts at the first time and ends at a second time, and the secondduration of time starts at the third time and ends at a fourth time.Also, the method includes, if the TRIAC dimmer is detected to beincluded in the lighting system and the TRIAC dimmer is thetrailing-edge TRIAC dimmer: in response to the first signal becominglarger than the first threshold in magnitude at a fifth time, causingthe second signal to ramp up and down during a duration of time. Theduration of time starts at a sixth time and ends at a seventh time. Theseventh time is a time when the first signal becomes smaller than thesecond threshold in magnitude.

Depending upon embodiment, one or more benefits may be achieved. Thesebenefits and various additional objects, features and advantages of thepresent invention can be fully appreciated with reference to thedetailed description and accompanying drawings that follow.

4. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows certain conventional timing diagrams for a leading-edgeTRIAC dimmer and a trailing-edge TRIAC dimmer.

FIG. 2 is a simplified diagram of a conventional lighting system thatincludes a bleeder.

FIG. 3 is a simplified diagram showing certain conventional componentsof the lighting system as shown in FIG. 2.

FIG. 4 shows certain conventional timing diagrams for the lightingsystem 200 as shown in FIGS. 2 and 3.

FIG. 5 is a simplified diagram of a lighting system according to anembodiment of the present invention.

FIG. 6A shows certain timing diagrams for the lighting system as shownin FIG. 5 if the TRIAC dimmer is a leading-edge TRIAC dimmer accordingto one embodiment of the present invention.

FIG. 6B shows certain timing diagrams for the lighting system as shownin FIG. 5 if the TRIAC dimmer is a trailing-edge TRIAC dimmer accordingto another embodiment of the present invention.

FIG. 7 shows certain dimming-control phase angle diagrams for thelighting system as shown in FIG. 5 according to certain embodiments ofthe present invention.

FIG. 8 is a simplified diagram showing certain components of thelighting system as shown in FIG. 5 according to one embodiment of thepresent invention.

FIG. 9A shows certain timing diagrams for the lighting system as shownin FIG. 5 and FIG. 6A if the TRIAC dimmer is a leading-edge TRIAC dimmeraccording to one embodiment of the present invention.

FIG. 9B shows certain timing diagrams for the lighting system as shownin FIG. 5 and FIG. 6B if the TRIAC dimmer is a trailing-edge TRIACdimmer according to another embodiment of the present invention.

5. DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the present invention are directed to integratedcircuits. More particularly, some embodiments of the invention provide asystem and method for stage-based control related to TRIAC dimmer.Merely by way of example, some embodiments of the invention have beenapplied to driving one or more light emitting diodes (LEDs). But itwould be recognized that the invention has a much broader range ofapplicability.

FIG. 5 is a simplified diagram of a lighting system according to anembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims. One of ordinaryskill in the art would recognize many variations, alternatives, andmodifications. The lighting system 500 includes a TRIAC dimmer 510, arectifier 520, a diode 526, capacitors 530, 532, 534, 536 and 538, amodulation controller 540, a winding 560, a transistor 562, resistors524, 570, 572, 574, 576, 578 and 579, and one or more LEDs 550. Forexample, the modulation controller 540 includes controller terminals542, 544, 546, 548, 552, 554, 556 and 558. In another example, themodulation controller 540 is a chip, and each of the controllerterminals 542, 544, 546, 548, 552, 554, 556 and 558 is a pin. In yetanother example, the modulation controller 540 is apulse-width-modulation (PWM) controller. In yet another example, thewinding 560 includes winding terminals 568 and 569.

In one embodiment, the TRIAC dimmer 510 receives an AC input voltage 514(e.g., VAC) and generates a voltage 512. For example, the voltage 512 isreceived by the rectifier 520 (e.g., a full wave rectifying bridge),which generates a rectified output voltage 522. In another example, therectified output voltage 522 is larger than or equal to zero.

In another embodiment, the resistor 579 includes resistor terminals 535and 539, and the capacitor 536 includes capacitor terminals 581 and 583.For example, the resistor terminal 535 receives the rectified outputvoltage 522. In another example, the resistor terminal 539 is connectedto the capacitor terminal 581, the controller terminal 552, and a gateterminal of the transistor 562. In yet another example, the gateterminal of the transistor 562 receives a gate voltage 537 from theresistor terminal 539, the capacitor terminal 581, and the controllerterminal 552. In yet another example, the capacitor terminal 583receives a ground voltage.

In yet another embodiment, the rectified output voltage 522 is used tocharge the capacitor 536 through the resistor 579 to raise the gatevoltage 537. For example, if the result of the gate voltage 537 minus asource voltage at a source terminal of the transistor 562 reaches orexceeds a transistor threshold voltage, the transistor 562 is turned on.

According to one embodiment, when the transistor 562 is turned on,through the transistor 562 and the controller terminal 554, a currentflows into the modulation controller 540 and uses an internal path tocharge the capacitor 532. For example, in response, the capacitor 532generates a capacitor voltage 533, which is received by the controllerterminal 544. In another example, if the capacitor voltage 533 reachesor exceeds an undervoltage-lockout threshold of the modulationcontroller 540, the modulation controller 540 starts up.

According to another embodiment, after the modulation controller 540 hasstarted up, a pulse-width-modulation (PWM) signal 555 is generated. Forexample, the PWM signal 555 has a signal frequency and a duty cycle. Inanother example, the PWM signal 555 is received by the source terminalof the transistor 562 through the controller terminal 554. In yetanother example, in response, the transistor 562 is turned on and off,in order to make an output current 566 constant and provide the outputcurrent 566 to the one or more LEDs 550, by working with at least thecapacitor 538.

In one embodiment, as shown in FIG. 5, a drain voltage at a drainterminal of the transistor 562 is received by a voltage divider thatincludes the resistors 576 and 578. For example, the drain terminal ofthe transistor 562 is connected to the winding terminal 569 of thewinding 560, and the winding terminal 568 of the winding 560 isconnected to the capacitor 530 and the resistor 579. In another example,in response to receiving the drain voltage, the voltage dividergenerates a voltage 577, which is received by the controller terminal556. In yet another example, the modulation controller 540 uses thevoltage 577 to detect the end of a demagnetization process of thewinding 560. In yet another example, the detection of the end of thedemagnetization process is used to control an internal error amplifierof the modulation controller 540, and through the controller terminal546, to control charging and discharging of the capacitor 534.

In another embodiment, after the modulation controller 540 has startedup, the resistor 574 is used to detect a current 561, which flowsthrough the winding 560. For example, the winding 560 is connected to adrain terminal of the transistor 562. In another example, the current561 flows from the winding 560 through the resistor 574, which inresponse generates a sensing voltage 575. In yet another example, thesensing voltage 575 is received by the controller terminal 558, and isprocessed by the modulation controller 540 on a cycle-by-cycle basis. Inyet another example, the peak magnitude of the sensing voltage 575 issampled, and the sampled signal is sent to an input terminal of theinternal error amplifier of the modulation controller 540. In yetanother example, the other input terminal of the internal erroramplifier receives a reference voltage V_(ref).

As shown in FIG. 5, the voltage 512 is received by the resistor 570according to one embodiment. For example, the resistors 570, 572, and524 together generates a voltage 571. In another example, the voltage571 is received by the controller terminal 542. In yet another example,the modulation controller 540 processes the voltage 571 and determinesphase angle of the voltage 571. According to yet another embodiment, thelighting system 500 does not include a bleeder. For example, thelighting system 500 ensures, without using any bleeder, that when theTRIAC dimmer 510 is fired on, an input current 564 that flows throughthe TRIAC dimmer 510 is larger than a holding current required by theTRIAC dimmer 510, in order to avoid misfire of the TRIAC dimmer 510 andalso avoid flickering of the one or more LEDs 550. In another example,the lighting system 500 does not use a bleeder, so heat generation isnot increased and energy efficiency of the lighting system 500 is notreduced.

In one embodiment, the lighting system 500 operates according to FIG. 6Aand/or FIG. 6B. For example, the lighting system 500 operates accordingto FIG. 6A. In another example, the lighting system 500 operatesaccording to FIG. 6B. In yet another example, the lighting system 500operates according to FIGS. 6A and 6B. In another embodiment, thelighting system 500 operates according to FIG. 7. In yet anotherembodiment, the lighting system 500 operates according to FIGS. 6A, 6B,and 7.

As discussed above and further emphasized here, FIG. 5 is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. For example, the lighting system 500 does not includethe TRIAC dimmer 510. In another example, the TRIAC dimmer 510 isremoved from the lighting system 500, and the AC input voltage 514(e.g., VAC) is directly received by the rectifier 520.

FIG. 6A shows certain timing diagrams for the lighting system 500 asshown in FIG. 5 if the TRIAC dimmer 510 is a leading-edge TRIAC dimmeraccording to one embodiment of the present invention. These diagrams aremerely examples, which should not unduly limit the scope of the claims.One of ordinary skill in the art would recognize many variations,alternatives, and modifications. The waveform 671 represents the voltage571 as a function of time, and the waveform 675 represents the sensingvoltage 575 as a function of time.

In one embodiment, each cycle of the voltage 571 has a phase angel(e.g., ϕ) that changes from ϕ_(i) to ϕ_(f). For example, ϕ_(i) is equalto 0°, and ϕ_(f) is equal to 180°. In another example, ϕ_(i) is equal to180°, and ϕ_(f) is equal to 360°. In yet another example, the voltage571 is larger than or equal to zero.

In another embodiment, the phase angel ϕ_(i) corresponds to time to, thephase angel ϕ_(c) corresponds to time t₂, and the phase angel ofcorresponds to time t₅. For example, a time duration T_(M) that startsfrom time t₀ and ends at time t₅ represents one period of the voltage571. In another example, a time duration that starts from time t₀ andends at time t₂ corresponds to ϕ_(dim_off). In yet another example, atime duration that starts from time t₂ and ends at time t₅ correspondsto ϕ_(dim_on).

In yet another embodiment, the TRIAC dimmer 510 is a leading-edge TRIACdimmer, which clips part of the waveform that corresponds to the phaseangel from ϕ_(i) to ϕ_(c). For example, ϕ_(c) is larger than or equal toϕ_(i) and is smaller than or equal to ϕ_(f). In another example, ϕ_(c)minus ϕ_(i) is equal to ϕ_(dim_off), which corresponds to a timeduration when the TRIAC dimmer 510 is not fired on.

In yet another embodiment, the unclipped part of the waveformcorresponds to the phase angel from ϕ_(c) to ϕ_(f). For example, ϕ_(f)minus ϕ_(c) is equal to ϕ_(dim_on), which corresponds to a time durationwhen the TRIAC dimmer 510 is fired on. In another example, ϕ_(dim_on)represents a dimming-control phase angle. In yet another example, thesum of ϕ_(dim_off) and ϕ_(dim_on) is equal to 180°.

In yet another example, ϕ_(dim_off) is larger than or equal to 0° andsmaller than or equal to 180°, and ϕ_(dim_on) is larger than or equal to0° and smaller than or equal to 180°. In yet another example, ifϕ_(dim_off) is equal to 180° and ϕ_(dim_on) is equal to 0°, the TRIACdimmer 510 clips the entire waveform that corresponds to the phase angelstarting at 0° and ending at 180° or starting at 1800 and ending at360°. In yet another example, if ϕ_(dim_off) is equal to 0° andϕ_(dim_on) is equal to 180°, the TRIAC dimmer 510 does not clip any partof the waveform that corresponds to the phase angel starting at 0° andending at 180° or starting at 180° and ending at 360°.

According to one embodiment, if the dimming-control phase angleϕ_(dim_on) becomes larger, the one or more LEDs 550 becomes brighter,and if the dimming-control phase angle ϕ_(dim_on) becomes smaller, theone or more LEDs 550 becomes dimmer. According to another embodiment, asshown by the waveform 675, for a particular dimming-control phase angleϕ_(dim_on), the sensing voltage 575 ramps up and down during a stage-1time duration T_(s1) and during a stage-2 time duration T_(s2). Forexample, during the stage-1 time duration T_(s1), within a switchingperiod (e.g., T_(sw1)), the sensing voltage 575 ramps up, ramps down,and then remains constant (e.g., remains equal to zero) until the end ofthe switching period (e.g., until the end of T_(sw1)). In anotherexample, during the stage-2 time duration T_(s2), within a switchingperiod (e.g., T_(sw2)), the sensing voltage 575 ramps up, ramps down,and then remains constant (e.g., remains equal to zero) until the end ofthe switching period (e.g., until the end of T_(sw2)). In yet anotherexample, the switching period T_(sw1) and the switching period T_(sw2)are equal in time duration.

According to yet another embodiment, corresponding to one period of thevoltage 571 (e.g., from time t₀ to time t₅), the stage-1 time durationT_(s1) starts at time t₂ and ends at time t₃, and the stage-2 timeduration T_(s2) starts at time t₄ and ends at time t₆. For example,corresponding to a previous period of the voltage 571 (e.g., a previousperiod ending at time to), the stage-2 time duration T_(s2) ends at timet₁. In another example, the time duration from time t₁ to time t₂ islonger than the switching period T_(sw1) and is also longer than theswitching period T_(sw2), and during the entire time duration from timet₁ to time t₂, the sensing voltage 575 remains constant (e.g., remainsequal to zero). In yet another example, the time duration from time t₃to time t₄ is longer than the switching period T_(sw1) and is alsolonger than the switching period T_(sw2), and during the entire timeduration from time t₃ to time t₄, the sensing voltage 575 remainsconstant (e.g., remains equal to zero).

According to yet another embodiment, time t₂ represents the time whenthe voltage 571 becomes larger than a threshold voltage V_(th1_a), andtime t₄ represents the time when the voltage 571 becomes smaller than athreshold voltage V_(th1_b). For example, the threshold voltageV_(th1_a) and the threshold voltage V_(th1_b) are equal. In anotherexample, the threshold voltage V_(th1_a) and the threshold voltageV_(th1_b) are not equal. According to yet another embodiment, time t₀represents the beginning time of one period of the voltage 571 that endsat time t₅, and time t₀ also represents the ending time of a previousperiod of the voltage 571. For example, during the previous period ofthe voltage 571, time t⁻¹ represents the time when the voltage 571becomes smaller than the threshold voltage V_(th1_b).

As discussed above and further emphasized here, FIG. 6A is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. For example, time t₅ is approximately equal to timet₄, and the phase angel ϕ_(f) approximately corresponds to time t₄. Inanother example, the time duration T_(M) starts at time t₀ and endsapproximately at time t₄, and the time duration T_(M) represents oneperiod of the voltage 571. In yet another example, a time duration thatstarts at time t₂ and ends at time t₄ approximately corresponds toϕ_(dim_on).

FIG. 6B shows certain timing diagrams for the lighting system 500 asshown in FIG. 5 if the TRIAC dimmer 510 is a trailing-edge TRIAC dimmeraccording to another embodiment of the present invention. These diagramsare merely examples, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The waveform 681 representsthe voltage 571 as a function of time, and the waveform 685 representsthe sensing voltage 575 as a function of time.

In one embodiment, each cycle of the voltage 571 has a phase angel(e.g., ϕ) that changes from ϕ_(i) to ϕ_(f). For example, ϕ_(i) is equalto 0°, and ϕf is equal to 180°. In another example, ϕ_(i) is equal to180°, and ϕ_(f) is equal to 360°. In yet another example, the voltage571 is larger than or equal to zero.

In another embodiment, the phase angel ϕ_(i) corresponds to time t₁₀,the phase angel ϕ_(c) corresponds to time t₁₃, and the phase angel ϕ_(f)corresponds to time t₁₅. For example, a time duration T_(M) that startsfrom time t₁₀ and ends at time t₁₅ represents one period of the voltage571. In another example, a time duration that starts from time t₁₀ andends at time t₁₃ corresponds to ϕ_(dim_on). In yet another example, atime duration that starts from time t₁₃ and ends at time t₁₅ correspondsto ϕ_(dim_off).

In yet another embodiment, the TRIAC dimmer 510 is a trailing-edge TRIACdimmer, which clips part of the waveform that corresponds to the phaseangel from ϕ_(c) to ϕ_(f). For example, ϕ_(c) is larger than or equal toϕ_(i) and is smaller than or equal to ϕ_(f). In another example, ϕ_(f)minus ϕ_(c) is equal to ϕ_(dim_off), which corresponds to a timeduration when the TRIAC dimmer 510 is not fired on.

In yet another embodiment, the unclipped part of the waveformcorresponds to the phase angel from ϕ_(i) to ϕ_(c). For example, ϕ_(c)minus ϕ_(i) is equal to ϕ_(dim_on), which corresponds to a time durationwhen the TRIAC dimmer 510 is fired on. In another example, ϕ_(dim_on)represents a dimming-control phase angle. In yet another example, thesum of ϕ_(dim_off) and ϕ_(dim_on) is equal to 180°.

In yet another example, ϕ_(dim_off) is larger than or equal to 0° andsmaller than or equal to 180°, and ϕ_(dim_on) is larger than or equal to0° and smaller than or equal to 180°. In yet another example, ifϕ_(dim_off) is equal to 180° and ϕ_(dim_on) is equal to 0°, the TRIACdimmer 510 clips the entire waveform that corresponds to the phase angelstarting at 0° and ending at 180° or starting at 180° and ending at360°. In yet another example, if ϕ_(dim_off) is equal to 0° and ϕ_(dim)is equal to 180°, the TRIAC dimmer 510 does not clip any part of thewaveform that corresponds to the phase angel starting at 0° and endingat 180° or starting at 180° and ending at 360°.

According to one embodiment, if the dimming-control phase angleϕ_(dim_on) becomes larger, the one or more LEDs 550 becomes brighter,and if the dimming-control phase angle ϕ_(dim_on) becomes smaller, theone or more LEDs 550 becomes dimmer. According to another embodiment, asshown by the waveform 685, for a particular dimming-control phase angleϕ_(dim_on), the sensing voltage 575 ramps up and down during a stage-1time duration T_(s1) and during a stage-2 time duration T_(s2). Forexample, the stage-1 time duration T_(s1) starts at time t₁₂ and ends attime t₁₃. In another example, the stage-2 time duration T_(s2) starts attime t₁₃ and ends at time t₁₄. In yet another example, the combinationof the stage-1 time duration T_(s1) and the stage-2 time duration T_(s2)starts at time t₁₂ and ends at time t₁₄.

According to yet another embodiment, during the time duration from timet₁₂ to time t₁₄, the sensing voltage 575 ramps up and down. For example,during the combination of the stage-1 time duration T_(s1) and thestage-2 time duration T_(s2), within a switching period (e.g.,T_(sw11)), the sensing voltage 575 ramps up, ramps down, and thenremains constant (e.g., remains equal to zero) until the end of theswitching period (e.g., T_(sw11)). In another example, during thecombination of the stage-1 time duration T_(s1) and the stage-2 timeduration T_(s2), within a switching period (e.g., T_(sw12)), the sensingvoltage 575 ramps up, ramps down, and then remains constant (e.g.,remains equal to zero) until the end of the switching period (e.g.,T_(sw12)).

According to yet another embodiment, time t₁₁ represents the time whenthe voltage 571 becomes larger than a threshold voltage V_(th2_a), andtime t₁₄ represents the time when the voltage 571 becomes smaller than athreshold voltage V_(th2_b). For example, the threshold voltageV_(th2_a) and the threshold voltage V_(th2_b) are equal. In anotherexample, the threshold voltage V_(th2_a) and the threshold voltageV_(th2_b) are not equal. In yet another example, the time duration fromtime till to time t₁₂ is longer than the switching period T_(sw11) andis also longer than the switching period T_(sw12), and during the entiretime duration from time till to time t₁₂, the sensing voltage 575remains constant (e.g., remains equal to zero). In yet another example,the time duration from time t₁₄ to time t₁₅ is longer than the switchingperiod T_(sw11) and is also longer than the switching period T_(sw12),and during the entire time duration from time t₁₄ to time t₁₅, thesensing voltage 575 remains constant (e.g., remains equal to zero).

As discussed above and further emphasized here, FIG. 6B is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. For example, time t₁₀ is approximately equal to timet₁₁, and the phase angel ϕ_(i) approximately corresponds to time t₁₁. Inanother example, the time duration T_(M) that starts at time till andends at time t₁₅ approximately represents one period of the voltage 571.In yet another example, a time duration that starts at time till andends at time t₁₃ approximately corresponds to ϕ_(dim_on).

FIG. 7 shows certain dimming-control phase angle diagrams for thelighting system 500 as shown in FIG. 5 according to certain embodimentsof the present invention. These diagrams are merely examples, whichshould not unduly limit the scope of the claims. One of ordinary skillin the art would recognize many variations, alternatives, andmodifications. The waveform 766 represents the output current 566 as afunction of dimming-control phase angle ϕ_(dim_on), the waveform 710represents the stage-1 time duration T_(s1) as a function ofdimming-control phase angle ϕ_(dim_on), the waveform 720 represents thestage-2 time duration T_(s2) as a function of dimming-control phaseangle ϕ_(dim_on), and the waveform 730 represents the two-stage totaltime duration T_(st) as a function of dimming-control phase angleϕ_(dim_on).

In one embodiment, as shown by the waveform 710, the stage-1 timeduration T_(s1) remains equal to T_(s1_min) if the dimming-control phaseangle ϕ_(dim_on) increases from 0° to ϕ_(A) and from ϕ_(A) to ϕ_(B), thestage-1 time duration T_(s1) increases (e.g., increases linearly at aconstant slope SL₁) from T_(s1_min) to T_(s1_max) if the dimming-controlphase angle ϕ_(dim_on) increases from ϕ_(B) to ϕ_(c), and the stage-1time duration T_(s1) remains equal to T_(s1_max) if the dimming-controlphase angle ϕ_(dim_on) increases from ϕ_(C) to 180°. For example,T_(s1_min) is equal to zero. In another example, T_(s1_min) is largerthan zero. In yet another example, T_(s1_max) is larger than T_(s1_min)and is also larger than zero.

In another embodiment, as shown by the waveform 720, the stage-2 timeduration T_(s2) remains equal to T_(s2_min) if the dimming-control phaseangle ϕ_(dim_on) increases from 0° to ϕ_(A), the stage-2 time durationT_(s2) increases (e.g., increases linearly at a constant slope SL₂) fromT_(s2_min) to T_(s2_max) if the dimming-control phase angle ϕ_(dim_on)increases from ϕ_(A) to ϕ_(B), and the stage-2 time duration T_(s2)remains equal to T_(s2_max) if the dimming-control phase angleϕ_(dim_on) increases from ϕ_(B) to ϕ_(C) and from ϕ_(C) to 180°. Forexample, the slope SL₁ and the slope SL₂ are different. In anotherexample, the slope SL₁ and the slope SL₂ are equal. In yet anotherexample, ϕ_(B) is smaller than 90°. In yet another example, T_(s2_min)is equal to zero. In yet another example, T_(s2_min) is larger thanzero. In yet another example, T_(s2_max) is larger than T_(s2_min) andis also larger than zero.

In yet another embodiment, as shown by the waveform 730, the two-stagetotal time duration T_(st) is equal to the sum of the stage-1 timeduration T_(s1) and the stage-2 time duration T_(s2). For example, thetwo-stage total time duration T_(st) remains equal to T_(st_min) if thedimming-control phase angle ϕ_(dim_on) increases from 0° to ϕ_(A), thetwo-stage total time duration T_(st) increases (e.g., increases linearlyat a slope STL₁) from T_(st_min) to T_(st_mid) if the dimming-controlphase angle ϕ_(dim_on) increases from ϕ_(A) to ϕ_(B), the two-stagetotal time duration T_(st) increases (e.g., increases linearly at aslope STL₂) from T_(st_mid) to T_(st_max) if the dimming-control phaseangle ϕ_(dim_on) increases from ϕ_(B) to ϕ_(C), and the two-stage totaltime duration T_(st) remains equal to T_(st_max) if the dimming-controlphase angle ϕ_(dim_on) increases from ϕ_(C) to 180°. For example, theslope STL₁ is equal to the slope SL₂, and the slope STL₂ is equal to theslope SL₁. In another example, the slope STL₁ and the slope STL₂ areequal. In yet another example, the slope STL₁ and the slope STL₂ are notequal. In yet another example, T_(st_min) is equal to the sum ofT_(s1_min) and T_(s2_min), T_(st_mid) is equal to the sum of T_(s1_min)and T_(s2_max), and T_(st_max) is equal to the sum of T_(s1_max) andT_(s2_max). In yet another example, T_(st_min) is equal to zero. In yetanother example, T_(st_min) is larger than zero. In yet another example,T_(st_mid) is larger than T_(st_min) and is also larger than zero, butis smaller than T_(st_max). In yet another example, T_(st_max) is largerthan T_(st_min) and T_(st_mid), and is also larger than zero.

In yet another embodiment, as shown by the waveform 766, the outputcurrent 566 remains equal to zero if the dimming-control phase angleϕ_(dim_on) increases from 0° to ϕ_(A), the output current 566 increases(e.g., increases linearly at a slope SL_(o_1)) from zero to I_(o_mid) ifthe dimming-control phase angle ϕ_(dim_on) increases from ϕ_(A) toϕ_(B), the output current 566 increases (e.g., increases linearly at aslope SL_(o_2)) from I_(o_mid) to I_(o_max) if the dimming-control phaseangle ϕ_(dim_on) increases from (B to (c, and the output current 566remains equal to I_(o_max) if the dimming-control phase angle ϕ_(dim_on)increases from ϕ_(C) to 180°. For example, the slope SL_(o_1) and theslope SL_(o_2) are different. In another example, the slope SL_(o_1) andthe slope SL_(o_2) are equal. In yet another example, I_(o_max) is equalto the magnitude of the output current 566 if the dimmer 510 is removedand the AC input voltage 514 (e.g., VAC) is directly received by therectifier 520. In yet another example, I_(o_mid) is smaller than 10% ofI_(o_max).

According to one embodiment, if the dimming-control phase angleϕ_(dim_on) increases from ϕ_(A) to ϕ_(B), the dimming control of the oneor more LEDs 550 is performed by changing the stage-2 time durationT_(s2), and if the dimming-control phase angle ϕ_(dim_on) increases fromϕ_(B) to ϕ_(C), the dimming control of the one or more LEDs 550 isperformed by changing the stage-1 time duration T_(s1). For example, theslope SL_(o_1) for the output current 566 depends on the slope SL₂ ofthe stage-2 time duration T_(s2). In another example, the slope SL_(o_2)for the output current 566 depends on the slope SL₁ of the stage-1 timeduration T_(s1).

According to another embodiment, magnitudes of ϕ_(A), ϕ_(B), and ϕ_(C)are adjusted, and 0°≤ϕ_(A)≤ϕ_(B)≤ϕ_(c)≤180° is satisfied. For example,magnitudes of ϕ_(A), ϕ_(B), and ϕ_(C) are adjusted, and0°<ϕ_(A)<ϕ_(B)<ϕ_(C)<180° is satisfied. In another example, magnitudesof ϕ_(A), ϕ_(B), and ϕ_(C) are adjusted, and 0°≤ϕ_(A)<ϕ_(B)<ϕ_(C)<180°is satisfied.

FIG. 8 is a simplified diagram showing certain components of thelighting system 500 as shown in FIG. 5 according to one embodiment ofthe present invention. This diagram is merely an example, which shouldnot unduly limit the scope of the claims. One of ordinary skill in theart would recognize many variations, alternatives, and modifications.The modulation controller 540 includes a dimming control component 800and a transistor 880. For example, the dimming control component 800includes a signal detector 810, a mode detector 850, a stage-timingsignal generator 860, a reference voltage generator 820, a modulationsignal generator 830, an AND gate 870, and a driver 840. For example,the modulation signal generator 830 is a pulse-width-modulation (PWM)signal generator.

As discussed above and further emphasized here, FIG. 8 is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. For example, the lighting system 500 does not includethe TRIAC dimmer 510. In another example, the TRIAC dimmer 510 isremoved from the lighting system 500, and the AC input voltage 514(e.g., VAC) is directly received by the rectifier 520.

In one embodiment, the mode detector 850 receives the voltage 571through the terminal 542, and determines, based at least in part on thevoltage 571, whether or not the TRIAC dimmer 510 is detected to beincluded in the lighting system 500 and if the TRIAC dimmer 510 isdetected to be included in the lighting system 500, whether the TRIACdimmer 510 is a leading-edge TRIAC dimmer or a trailing-edge TRIACdimmer. For example, the mode detector 850 generates a mode signal 852that indicates whether or not the TRIAC dimmer 510 is detected to beincluded in the lighting system 500 and if the TRIAC dimmer 510 isdetected to be included in the lighting system 500, whether the TRIACdimmer 510 is a leading-edge TRIAC dimmer or a trailing-edge TRIACdimmer. In another example, the mode signal 852 is received by thereference voltage generator 820 and the stage-timing signal generator860.

In yet another example, the mode signal 852 includes three logic signals852 a, 852 b, and 852 c. In yet another example, if the logic signal 852a is at the logic high level and the logic signals 852 b and 852 c areat the logic low level, the mode signal 852 indicates that the TRIACdimmer 510 is not included in the lighting system 500. In yet anotherexample, if the logic signal 852 b is at the logic high level and thelogic signals 852 a and 852 c are at the logic low level, the modesignal 852 indicates that the TRIAC dimmer 510 is detected to beincluded in the lighting system 500 and the TRIAC dimmer 510 is aleading-edge TRIAC dimmer. In yet another example, if the logic signal852 c is at the logic high level and the logic signals 852 a and 852 bare at the logic low level, the mode signal 852 indicates that the TRIACdimmer 510 is detected to be included in the lighting system 500 and theTRIAC dimmer 510 is a trailing-edge TRIAC dimmer.

In another embodiment, the signal detector 810 receives the voltage 571through the terminal 542, detects the voltage 571, and generates asignal 812. For example, the signal 812 indicates approximately themagnitude of the dimming-control phase angle ϕ_(dim_on) of the voltage571 (e.g., as shown in FIG. 6A, FIG. 6B, and/or FIG. 7).

In yet another embodiment, the signal detector 810 generates the signal812 based at least in part on the voltage 571. For example, if thevoltage 571 becomes larger than a threshold voltage V_(th_aa), thesignal 812 changes from a logic low level to a logic high level. Inanother example, if the voltage 571 becomes smaller than a thresholdvoltage V_(th_bb), the signal 812 changes from the logic high level tothe logic low level. In yet another example, the threshold voltageV_(th_aa) and the threshold voltage V_(th_bb) are equal. In yet anotherexample, the threshold voltage V_(th_aa) and the threshold voltageV_(th_bb) are not equal.

According to one embodiment, as shown in FIG. 6A, the signal 812 changesfrom the logic high level to the logic low level at time t⁻¹, remains atthe logic low level from time t⁻¹ to time t₂, changes from the logic lowlevel to the logic high level at time t₂, remains at the logic highlevel from time t₂ to time t₄, changes from the logic high level to thelogic low level at time t₄, and remains at the logic low level from timet₄ to time t₅. For example, the threshold voltage V_(th_aa) is thethreshold voltage V_(th1_a). In another example, the threshold voltageV_(th_bb) is the threshold voltage V_(th1_b).

According to another embodiment, as shown in FIG. 6B, the signal 812remains at the logic low level from time t₁₀ to time t₁₁, changes fromthe logic low level to the logic high level at time t₁₁, remains at thelogic high level from time till to time t₁₄, changes from the logic highlevel to the logic low level at time t₁₄, and remains at the logic lowlevel from time t₁₄ to time t₁₅. For example, the threshold voltageV_(th_aa) is the threshold voltage V_(th2_a). In another example, thethreshold voltage V_(th_bb) is the threshold voltage V_(th2_b).

According to some embodiments, the reference voltage generator 820receives the mode signal 852 and the signal 812, and generates areference voltage 822 (e.g., V_(ref)). In one embodiment, if the modesignal 852 indicates that the TRIAC dimmer 510 is not included in thelighting system 500, the reference voltage generator 820 generates thereference voltage 822 (e.g., V_(ref)) that is a predetermined constant,regardless of the magnitude of the dimming-control phase angleϕ_(dim_on).

In another embodiment, if the mode signal 852 indicates that the TRIACdimmer 510 is detected to be included in the lighting system 500 and theTRIAC dimmer 510 is a leading-edge TRIAC dimmer, the reference voltagegenerator 820 generates the reference voltage 822 (e.g., V_(ref)). Forexample, the reference voltage 822 (e.g., V_(ref)) is a predeterminedconstant, regardless of the magnitude of the dimming-control phase angleϕ_(dim_on). In another example, the reference voltage 822 (e.g.,V_(ref)) changes with the magnitude of the dimming-control phase angleϕ_(dim_on). In yet another example, the reference voltage 822 (e.g.,V_(ref)) increases proportionally with the increasing magnitude of thedimming-control phase angle ϕ_(dim_on).

In yet another embodiment, if the mode signal 852 indicates that theTRIAC dimmer 510 is detected to be included in the lighting system 500and the TRIAC dimmer 510 is a trailing-edge TRIAC dimmer, the referencevoltage generator 820 generates the reference voltage 822 (e.g.,V_(ref)). For example, the reference voltage 822 (e.g., V_(ref)) is apredetermined constant, regardless of the magnitude of thedimming-control phase angle ϕ_(dim_on). In another example, thereference voltage 822 (e.g., V_(ref)) changes with the magnitude of thedimming-control phase angle ϕ_(dim_on). In yet another example, thereference voltage 822 (e.g., V_(ref)) increases proportionally with theincreasing magnitude of the dimming-control phase angle ϕ_(dim_on).

In yet another embodiment, the reference voltage 822 (e.g., V_(ref))when the mode signal 852 indicates that the TRIAC dimmer 510 is notincluded in the lighting system 500 is smaller than the referencevoltage 822 (e.g., V_(ref)) when the mode signal 852 indicates that theTRIAC dimmer 510 is detected to be included in the lighting system 500.

According to certain embodiments, the reference voltage 822 (e.g.,V_(ref)) is received by the modulation signal generator 830, which alsoreceives the sensing voltage 575 through the terminal 558. For example,the sensing voltage 575 represents the magnitude of the current 561,which flows through the winding 560 and the resistor 574.

In one embodiment, the modulation signal generator 830 processes thereference voltage 822 (e.g., V_(ref)) and the sensing voltage 575 andgenerates a modulation signal 832. For example, the modulation signalgenerator 830 is a pulse-width-modulation (PWM) signal generator, andthe modulation signal 832 is a pulse-width-modulation (PWM) signal. Inanother example, within each switching cycle, the modulation signalgenerator 830 determines an integral of the reference voltage 822 (e.g.,V_(ref)) over time, converts the integral to an intermediate voltagethat is proportional to the integral, and determines whether the sensingvoltage 575 reaches or exceeds the intermediate voltage. In yet anotherexample, within each switching cycle, if the sensing voltage 575 reachesor exceeds the intermediate voltage, the modulation signal generator 830changes the modulation signal 832 from a logic high level to a logic lowlevel to cause the end of the pulse width for the switching cycle if thepulse width is not larger than the maximum pulse width predetermined bythe modulation controller 540. In yet another example, if the rectifiedoutput voltage 522 is large, within each switching cycle, the sensingvoltage 575 reaches or exceeds the intermediate voltage fast enough sothat the pulse width ends before the pulse width becomes larger than amaximum pulse width predetermined by the modulation controller 540. Inyet another example, if the rectified output voltage 522 is small (e.g.,if the capacitor 530 has been completely discharged), within eachswitching cycle, the sensing voltage 575 cannot reach or exceed theintermediate voltage fast enough, and the pulse width of the modulationsignal 832 for the switching cycle is set equal to the maximum pulsewidth predetermined by the modulation controller 540. In yet anotherexample, the modulation signal 832 is received by the AND gate 870.

In another embodiment, the modulation signal generator 830 processes thesensing voltage 575, detects whether the capacitor 530 has beencompletely discharged based at least in part on the sensing voltage 575,and when the capacitor 530 has been detected to be completelydischarged, generate a timing signal 834 that indicates the capacitor530 has been completely discharged. For example, the timing signal 834indicates the capacitor 530 becomes completely discharged at time t₆ asshown in FIG. 6A. In another example, the timing signal 834 is receivedby the stage-timing signal generator 860.

In yet another embodiment, the modulation signal generator 830 processesthe sensing voltage 575, detects whether a pulse width of the modulationsignal 832 for a switching cycle is set equal to the maximum pulse widthpredetermined by the modulation controller 540, and if the pulse widthof the modulation signal 832 is set equal to the maximum pulse width,generate the timing signal 834 that indicates the capacitor 530 has beencompletely discharged. For example, the timing signal 834 indicates thecapacitor 530 becomes completely discharged at time t₆ as shown in FIG.6A. In another example, the timing signal 834 is received by thestage-timing signal generator 860.

According to some embodiments, the stage-timing signal generator 860receives the mode signal 852, the signal 812 and the timing signal 834and generates a stage-timing signal 862 based at least in part on themode signal 852, the signal 812 and/or the timing signal 834. Forexample, the stage-timing signal 862 is received by the AND gate 870.

In one embodiment, as shown in FIG. 6A, if the mode signal 852 indicatesthe TRIAC dimmer 510 is detected to be included in the lighting system500 and the TRIAC dimmer 510 is a leading-edge TRIAC dimmer, thestage-timing signal 862 indicates the beginning and the end of thestage-1 time duration T_(s1) and the beginning and the end of thestage-2 time duration T_(s2). For example, the stage-timing signalgenerator 860 changes the stage-timing signal 862 from the logic lowlevel to the logic high level at time t₂, indicating the beginning ofthe stage-1 time duration T_(s1). In another example, the stage-timingsignal generator 860 changes the stage-timing signal 862 from the logichigh level to the logic low level at time t₃, indicating the end of thestage-1 time duration T_(s1), if the stage-1 time duration T_(s1) is notlarger than T_(s1_max) in magnitude as shown by the waveform 710 of FIG.7. In yet another example, the stage-timing signal generator 860 changesthe stage-timing signal 862 from the logic low level to the logic highlevel at time t₄, indicating the beginning of the stage-2 time durationT_(s2). In another example, the stage-timing signal generator 860changes the stage-timing signal 862 from the logic high level to thelogic low level at time t₆, indicating the end of the stage-2 timeduration T_(s2), if the stage-2 time duration T_(s2) is not larger thanT_(s2_max) in magnitude as shown by the waveform 720 of FIG. 7.

In another embodiment, as shown in FIG. 6B, if the mode signal 852indicates the TRIAC dimmer 510 is detected to be included in thelighting system 500 and the TRIAC dimmer 510 is a trailing-edge TRIACdimmer, the stage-timing signal 862 indicates the beginning of thestage-1 time duration T_(s1) and the end of the stage-2 time durationT_(s2). For example, the stage-timing signal generator 860 changes thestage-timing signal 862 from the logic low level to the logic high levelat time t₁₂, indicating the beginning of the stage-1 time durationT_(s1). In another example, the stage-timing signal generator 860changes the stage-timing signal 862 from the logic high level to thelogic low level at time t₁₄, indicating the end of the stage-2 timeduration T_(s2). In yet another example, the stage-1 time durationT_(s1) is not larger than T_(s1_max) in magnitude as shown by thewaveform 710 of FIG. 7, and the stage-2 time duration T_(s2) is notlarger than T_(s2_max) in magnitude as shown by the waveform 720 of FIG.7.

In yet another embodiment, if the mode signal 852 indicates the TRIACdimmer 510 is not included in the lighting system 500, the stage-timingsignal 862 is the same as the signal 812. For example, if the voltage571 becomes larger than the threshold voltage V_(th_aa), thestage-timing signal 862 changes from the logic low level to the logichigh level. In another example, if the voltage 571 becomes smaller thanthe threshold voltage V_(th_bb), the stage-timing signal 862 changesfrom the logic high level to the logic low level. In yet anotherexample, the stage-timing signal 862 remains at the logic high levelfrom a time when the voltage 571 becomes larger than the thresholdvoltage V_(th_aa) to a time when the voltage 571 becomes smaller thanthe threshold voltage V_(th_bb) for the first time since the voltage 571becomes larger than the threshold voltage V_(th_aa). In yet anotherexample, the stage-timing signal 862 remains at the logic low level froma time when the voltage 571 becomes smaller than the threshold voltageV_(th_bb) to a time when the voltage 571 becomes larger than thethreshold voltage V_(th_aa) for the first time since the voltage 571becomes smaller than the threshold voltage V_(th_bb).

According to certain embodiments, the AND gate 870 receives themodulation signal 832 and the stage-timing signal 862 and generates acontrol signal 872 based at least in part on the modulation signal 832and the stage-timing signal 862. In one embodiment, if the mode signal852 indicates the TRIAC dimmer 510 is included in the lighting system500, the stage-timing signal 862 remains at the logic high level duringthe stage-1 time duration T_(s1) and during the stage-2 time durationT_(s2), and the stage-timing signal 862 remains at the logic low leveloutside the stage-1 time duration T_(s1) and the stage-2 time durationT_(s2). For example, if the mode signal 852 indicates the TRIAC dimmer510 is included in the lighting system 500, during the stage-1 timeduration T_(s1) and during the stage-2 time duration T_(s2), the controlsignal 872 is the same as the modulation signal 832. In another example,if the mode signal 852 indicates the TRIAC dimmer 510 is included in thelighting system 500, outside the stage-1 time duration T_(s1) and thestage-2 time duration T_(s2), the control signal 872 remains at thelogic low level.

According to some embodiments, if the mode signal 852 indicates theTRIAC dimmer 510 is not included in the lighting system 500, thestage-timing signal 862 remains at the logic high level throughoutentire each half cycle of the voltage 571. In one embodiment, thevoltage 571 has a phase angel (e.g., 0), which changes from 0° to 180°for a half cycle of the voltage 571 and then changes from 180° to 360°for another half cycle of the voltage 571. In another embodiment, if themode signal 852 indicates the TRIAC dimmer 510 is not included in thelighting system 500, the control signal 872 is the same as themodulation signal 832. In yet another embodiment, if the mode signal 852indicates the TRIAC dimmer 510 is not included in the lighting system500, the modulation signal generator 830 operates under quasi-resonant(QR) constant-current (CC) mode. For example, under the quasi-resonant(QR) constant-current (CC) mode, each half cycle of the voltage 571includes multiple switching cycles of the modulation signal 832. Inanother example, each switching cycle of the modulation signal 832includes an on-time period and an off-time period. In yet anotherexample, during each half cycle of the voltage 571, the on-time periodof the modulation signal 832 remains constant in magnitude but theoff-time period of the modulation signal 832 changes in magnitude, inorder to achieve satisfactory power factor (PF).

According to one embodiment, the driver 840 receives the control signal872 and generates a drive signal 842. For example, if the control signal872 is at the logic high level, the drive signal 842 is also at thelogic high level. In another example, if the control signal 872 is atthe logic low level, the drive signal 842 is also at the logic lowlevel. In yet another example, the driver 840 outputs the drive signal842 to the transistor 880.

According to another embodiment, the transistor 880 is turned on if thedrive signal 842 is at the logic high level, and the transistor 880 isturned off if the drive signal 842 is at the logic low level. Forexample, when the transistor 562 and the transistor 880 are turned on,the current 561 flows through the winding 560, the transistor 562, thecontroller terminal 554, the transistor 880, the controller terminal558, and the resistor 574. In another example, if the transistor 880becomes turned off when the transistor 562 is still turned on, thetransistor 562 also becomes turned off and the winding 560 starts todischarge. In yet another example, if the transistor 880 becomes turnedon when the transistor 562 is still turned off, the transistor 562 alsobecomes turned on and the winding 560 starts to charge.

As shown in FIGS. 5 and 8, the lighting system 500 includes aquasi-resonant system with a buck-boost topology according to certainembodiments. For example, the output current 566 of the quasi-resonantsystem is received by the one or more LEDs 550 and is determined asfollows:

$\begin{matrix}{I_{o} = {\frac{1}{2} \times \frac{V_{ref}}{R_{cs}} \times \frac{T_{s1} + T_{s2}}{T_{M}}}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$where I_(o) represents the output current 566 of the quasi-resonantsystem of the lighting system 500. Additionally, V_(ref) represents thereference voltage 822 (e.g., the reference voltage received by aninternal error amplifier of the modulation controller 540), and R_(cs)represents the resistance of the resistor 574. Moreover, T_(s1)represents a stage-1 time duration, and T_(s2) represents a stage-2 timeduration. Also, T_(M) represents one period of the voltage 571. Forexample, one period of the voltage 571 is equal to half period of the ACinput voltage 514 (e.g., VAC).

FIG. 9A shows certain timing diagrams for the lighting system 500 asshown in FIG. 5 and FIG. 6A if the TRIAC dimmer 510 is a leading-edgeTRIAC dimmer according to one embodiment of the present invention. Thesediagrams are merely examples, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. The waveform 671 representsthe voltage 571 as a function of time as shown in FIG. 6A, the waveform675 represents the sensing voltage 575 as a function of time as shown inFIG. 6A, and the waveform 962 represents the stage-timing signal 862 asa function of time.

In one embodiment, the TRIAC dimmer 510 is a leading-edge TRIAC dimmer,which clips part of the waveform that corresponds to the phase angelfrom ϕ_(i) to ϕ_(c). For example, ϕ_(c) minus ϕ_(i) is equal toϕ_(dim_off), which corresponds to a time duration (e.g., T_(dim_off))when the TRIAC dimmer 510 is not fired on. In another embodiment, theunclipped part of the waveform corresponds to the phase angel from ϕ_(c)to ϕ_(f). For example, ϕ_(f) minus ϕ_(c) is equal to ϕ_(dim_on), whichcorresponds to a time duration (e.g., T_(dim_on)) when the TRIAC dimmer510 is fired on.

In another embodiment, time t₅ is approximately equal to time t₄, andthe phase angel ϕ_(f) approximately corresponds to time t₄. For example,the time duration T_(dim_off) when the TRIAC dimmer 510 is not fired onstarts at time t₀ and ends at t₂. In another example, the time durationT_(dim_on) when the TRIAC dimmer 510 is fired on starts at time t₂ andends approximately at t₄. In yet another example, one period T_(M) ofthe voltage 571 starts at time t₀ and ends approximately at time t₄.

In yet another embodiment, one period T_(M) of the voltage 571 isdetermined as follows:T _(M) =T _(dim_off) +T _(dim_on)  (Equation 3)where T_(M) represents one period of the voltage 571. Additionally,T_(dim_off) represents a time duration when the TRIAC dimmer 510 is notfired on, and T_(dim_on) represents a time duration when the TRIACdimmer 510 is fired on.

According to one embodiment, the stage-1 time duration T_(s1) starts attime t₂ and ends at time t₃. For example, as shown by the waveform 962,the stage-timing signal 862 changes from a logic low level to a logichigh level at time t₂, remains at the logic high level from time t₂ totime t₃, and changes from the logic high level back to the logic lowlevel at time t₃.

According to another embodiment, the stage-2 time duration T_(s2) startsat time t₄ and ends at time t₆. For example, as shown by the waveform962, the stage-timing signal 862 changes from the logic low level to thelogic high level at time t₄, remains at the logic high level from timet₄ to time t₆, and changes from the logic high level back to the logiclow level at time t₆. In another example, time t₄ is after time t₃.

In one embodiment, the stage-1 time duration T_(s1) starts at time t₂,which is the end of the time duration T_(dim_off) when the TRIAC dimmer510 is not fired on. For example, the signal 812 changes from the logiclow level to the logic high at time t₂, and in response, thestage-timing signal generator 860 changes the stage-timing signal 862from the logic low level to the logic high level at time t₂, indicatingthe beginning of the stage-1 time duration T_(s1).

In another embodiment, the stage-1 time duration T_(s1) ends at time t₃,which is the end of a predetermined time duration T_(P) from the timewhen the voltage 571 becomes smaller than the threshold voltageV_(th1_b). For example, the signal 812 changes from the logic high levelto the logic low level at time t⁻¹, and in response, the stage-timingsignal generator 860, after the predetermined time duration T_(P),changes the stage-timing signal 862 from the logic high level to thelogic low level at time t₃, indicating the end of the stage-1 timeduration T_(s1).

In yet another embodiment, the stage-1 time duration T_(s1) is largerthan or equal to zero but smaller than or equal to T_(s1_max) inmagnitude, as shown by the waveform 710 of FIG. 7. For example, time t₃is larger than or equal to time t₂ in magnitude. In another example,time t₃ minus time t₂ is smaller than or equal to T_(s1_max) inmagnitude.

According to one embodiment, as shown in FIG. 9A, time t⁻¹ isapproximately equal to time t₄, and the following can be obtained:T _(dim_off) +T _(s1) ≈T _(P)  (Equation 4)where T_(dim_off) represents the time duration when the TRIAC dimmer 510is not fired on, and T_(s1) represents a stage-1 time duration.Additionally, T_(P) represents a predetermined time duration. Forexample, the stage-1 time duration T_(s1) satisfies Equation 4, and thestage-1 time duration T_(s1) is also larger than or equal to zero butsmaller than or equal to T_(s1_max) in magnitude as shown by thewaveform 710 of FIG. 7.

According to another embodiment, based on Equations 3 and 4, thefollowing can be obtained:T _(s1) ≈T _(dim_on)−(T _(M) −T _(P))  (Equation 5)where T_(s1) represents the stage-1 time duration, and T_(dim_on)represents the time duration when the TRIAC dimmer 510 is fired on.Additionally, T_(M) represents one period of the voltage 571, and T_(P)represents a predetermined time duration. For example, the stage-1 timeduration T_(s1) satisfies Equation 5, and the stage-1 time durationT_(s1) is also larger than zero but smaller than T_(s1_max) as shown bythe waveform 710 of FIG. 7.

According to yet another embodiment, a time duration when the TRIACdimmer 510 is fired on has the following relationship with adimming-control phase angle:T _(dim_on) =k×ϕ _(dim_on)  (Equation 6)where T_(dim_on) represents the time duration when the TRIAC dimmer 510is fired on, and ϕ_(dim_on) represents the dimming-control phase angle.Additionally, k represents a constant. For example, based on Equations 5and 6, the following can also be obtained:T _(s1) ≈k×ϕ _(dim_on)−(T _(M) −T _(P))  (Equation 7)where T_(s1) represents the stage-1 time duration, and ϕ_(dim_on)represents the dimming-control phase angle. Additionally, k represents aconstant. Moreover, T_(M) represents one period of the voltage 571, andT_(P) represents a predetermined time duration. In another example, thestage-1 time duration T_(s1) satisfies Equation 7, and the stage-1 timeduration T_(s1) is also larger than or equal to zero but smaller than orequal to T_(s1_max) in magnitude, as shown by the waveform 710 of FIG.7.

In one embodiment, the stage-2 time duration T_(s2) starts at time t₄.For example, the signal 812 changes from the logic high level to thelogic low at time t₄, and in response, the stage-timing signal generator860 changes the stage-timing signal 862 from the logic low level to thelogic high level at time t₄, indicating the beginning of the stage-2time duration T_(s2).

In another embodiment, the stage-2 time duration T_(s2) ends at time t₆,which is the time when the capacitor 530 is completely discharged. Forexample, the timing signal 834 indicates that the capacitor 530 becomescompletely discharged at time t₆, and in response, the stage-timingsignal generator 860 changes the stage-timing signal 862 from the logichigh level to the logic low level at time t₆, indicating the end of thestage-2 time duration T_(s2).

In yet another embodiment, the stage-2 time duration T_(s2) is largerthan or equal to zero but smaller than or equal to T_(s2_max) inmagnitude, as shown by the waveform 720 of FIG. 7. For example, time t₆is larger than or equal to time t₄ in magnitude. In another example,time t₆ minus time t₄ is smaller than or equal to T_(s2_max) inmagnitude.

As shown in FIG. 9A, corresponding to each period (e.g., correspondingto each T_(M)) of the voltage 571, there are a stage-1 time duration(e.g., T_(s1)) and a stage-2 time duration (e.g., T_(s2)) according tocertain embodiments. In one embodiment, corresponding to one period ofthe voltage 571 (e.g., from time t₀ to time t₅), the stage-1 timeduration T_(s1) starts at time t₂ and ends at time t₃, and the stage-2time duration T_(s2) starts at time t₄ and ends at time t₆. In anotherembodiment, corresponding to a previous period of the voltage 571 (e.g.,ending at time to), the stage-2 time duration T_(s2) starts at time t⁻¹and ends at time t₁.

In yet another embodiment, the stage-timing signal 862 changes from thelogic low level to the logic high level at time t⁻¹, remains at thelogic high level from time t⁻¹ to time t₁, changes from the logic highlevel to the logic low level at time t₁, remains at the logic low levelfrom time t₁ to time t₂, changes from the logic low level to the logichigh level at time t₂, remains at the logic high level from time t₂ totime t₃, changes from the logic high level to the logic low level attime t₃, remains at the logic low level from time t₃ to time t₄, changesfrom the logic low level to the logic high level at time t₄, remains atthe logic high level from time t₄ to t₆, and changes from the logic highlevel to the logic low level at time t₆.

According to one embodiment, corresponding to one period of the voltage571 (e.g., from time t₀ to time t₅), the stage-1 time duration (e.g.,T_(s1) from time t₂ to time t₃) falls within the time duration when theTRIAC dimmer 510 is fired on (e.g., T_(dim_on) from time t₂ to time t₅),and the stage-2 time duration (e.g., T_(s2) from time t₄ to time t₆) atleast mostly falls outside of the time duration when the TRIAC dimmer510 is fired on (e.g., T_(dim_on) from time t₂ to time t₅). For example,corresponding to the period of the voltage 571 (e.g., from time t₀ totime t₅), during the stage-1 time duration (e.g., T_(s1)) and during thestage-2 time duration (e.g., T_(s2)), the sensing voltage 575 ramps upand down and the current 561 also ramps up and down. In another example,corresponding to the period of the voltage 571 (e.g., from time t₀ totime t₅), outside the stage-1 time duration (e.g., T_(s1)) and thestage-2 time duration (e.g., T_(s2)), the sensing voltage 575 remainsequal to zero. In yet another example, corresponding to the period ofthe voltage 571 (e.g., from time t₀ to time t₅), outside the stage-1time duration (e.g., T_(s1)) and the stage-2 time duration (e.g.,T_(s2)), the current 561 charges the capacitor 532. According to anotherembodiment, corresponding to a previous period of the voltage 571 (e.g.,ending at time t₅), during the stage-2 time duration T_(s2) (e.g.,starting at time t⁻¹ and ending at time t₁), the sensing voltage 575ramps up and down and the current 561 also ramps up and down.

FIG. 9B shows certain timing diagrams for the lighting system 500 asshown in FIG. 5 and FIG. 6B if the TRIAC dimmer 510 is a trailing-edgeTRIAC dimmer according to another embodiment of the present invention.These diagrams are merely examples, which should not unduly limit thescope of the claims. One of ordinary skill in the art would recognizemany variations, alternatives, and modifications. The waveform 681represents the voltage 571 as a function of time as shown in FIG. 6B,the waveform 675 represents the sensing voltage 575 as a function oftime as shown in FIG. 6B, and the waveform 972 represents thestage-timing signal 862 as a function of time.

In one embodiment, the TRIAC dimmer 510 is a trailing-edge TRIAC dimmer,which clips part of the waveform that corresponds to the phase angelfrom ϕ_(c) to ϕ_(f). For example, ϕ_(f) minus ϕ_(c) is equal toϕ_(dim_off), which corresponds to a time duration (e.g., T_(dim_off))when the TRIAC dimmer 510 is not fired on. In another embodiment, theunclipped part of the waveform corresponds to the phase angel from ϕ_(i)to ϕ_(c). For example, ϕ_(c) minus ϕ_(i) is equal to ϕ_(dim_on), whichcorresponds to a time duration (e.g., T_(dim_on)) when the TRIAC dimmer510 is fired on.

In another embodiment, time t₁₀ is approximately equal to time t₁₁, andthe phase angel ϕ_(i) approximately corresponds to time t₁₁. Forexample, the time duration T_(dim_off) when the TRIAC dimmer 510 is notfired on starts at time t₁₃ and ends at t₁₅. In another example, thetime duration T_(dim_on) when the TRIAC dimmer 510 is fired on starts atapproximately time till and ends at t₁₃. In yet another example, oneperiod T_(M) of the voltage 571 starts approximately at time till andends at time t₁₅.

In yet another embodiment, one period T_(M) of the voltage 571 isdetermined as follows:T _(M) =T _(dim_off) +T _(dim_on)  (Equation 8)where T_(M) represents one period of the voltage 571. Additionally,T_(dim_off) represents a time duration when the TRIAC dimmer 510 is notfired on, and ϕ_(dim_on) represents a time duration when the TRIACdimmer 510 is fired on.

According to one embodiment, the stage-1 time duration T_(s1) starts attime t₁₂ and ends at time t₁₃. For example, as shown by the waveform972, the stage-timing signal 862 changes from a logic low level to alogic high level at time t₁₂, remains at the logic high level from timet₁₂ to time t₁₃. According to another embodiment, the stage-2 timeduration T_(s2) starts at time t₁₃ and ends at time t₁₄. For example, asshown by the waveform 972, the stage-timing signal 862 remains at thelogic high level from time t₁₃ to time t₁₄, and changes from the logichigh level back to the logic low level at time t₁₄. According to yetanother embodiment, the combination of the stage-1 time duration T_(s1)and the stage-2 time duration T_(s2) starts at time t₁₂ and ends at timet₁₄. For example, as shown by the waveform 972, the stage-timing signal862 changes from the logic low level to the logic high level at timet₁₂, remains at the logic high level from time t₁₂ to time t₁₄, andchanges from the logic high level back to the logic low level at timet₁₄.

In one embodiment, the stage-1 time duration T_(s1) starts at time t₁₂,which is the end of a predetermined time duration T_(Q) from the timewhen the voltage 571 becomes larger than the threshold voltageV_(th2_a). For example, the phase signal 812 changes from the logic lowlevel to the logic high level at time t₁₁, and in response, thestage-timing signal generator 860, after the predetermined time durationT_(Q), changes the stage-timing signal 862 from the logic low level tothe logic high level at time t₁₂, indicating the beginning of thestage-1 time duration T_(s1).

In another embodiment, the stage-1 time duration T_(s1) ends at timet₁₂, which is the end of the time duration T_(dim_on) when the TRIACdimmer 510 is fired on. For example, the stage-1 time duration T_(s1) islarger than or equal to zero but smaller than or equal to T_(s1_max) inmagnitude, as shown by the waveform 710 of FIG. 7. For example, time t₁₃is larger than or equal to time t₁₂ in magnitude. In another example,time t₁₃ minus time t₁₂ is smaller than or equal to T_(s1_max) inmagnitude.

According to one embodiment, as shown in FIG. 9B, the following can beobtained:T _(Q) +T _(s1) ≈T _(dim_on)  (Equation 9)where T_(Q) represents a predetermined time duration, and T_(s1)represents a stage-1 time duration. Additionally, T_(dim_on) representsthe time duration when the TRIAC dimmer 510 is fired on. For example,the stage-1 time duration T_(s1) satisfies Equation 9, and the stage-1time duration T_(s1) is also larger than or equal to zero but smallerthan or equal to T_(s1_max) in magnitude as shown by the waveform 710 ofFIG. 7.

According to another embodiment, based on Equation 9, the following canbe obtained:T _(s1) ≈T _(dim_on) −T _(Q)  (Equation 10)where T_(s1) represents the stage-1 time duration, and T_(dim_on)represents the time duration when the TRIAC dimmer 510 is fired on.Additionally, T_(Q) represents a predetermined time duration. Forexample, the stage-1 time duration T_(s1) satisfies Equation 10, and thestage-1 time duration T_(s1) is also larger than zero but smaller thanT_(s1_max) as shown by the waveform 710 of FIG. 7.

According to yet another embodiment, a time duration when the TRIACdimmer 510 is fired on has the following relationship with adimming-control phase angle:T _(dim_on) =k×ϕ _(dim_on)  (Equation 11)where T_(dim_on) represents the time duration when the TRIAC dimmer 510is fired on, and ϕ_(dim_on) represents the dimming-control phase angle.Additionally, k represents a constant. For example, based on Equations10 and 11, the following can also be obtained:T _(s1) ≈k×ϕ _(dim_on) −T _(Q)  (Equation 12)where T_(s1) represents the stage-1 time duration, and ϕ_(dim_on)represents the dimming-control phase angle. Additionally, k represents aconstant, and T_(Q) represents a predetermined time duration. In anotherexample, the stage-1 time duration T_(s1) satisfies Equation 12, and thestage-1 time duration T_(s1) is also larger than or equal to zero butsmaller than or equal to T_(s1_max) in magnitude, as shown by thewaveform 710 of FIG. 7.

In one embodiment, the stage-2 time duration T_(s2) starts at time t₁₃,which is the end of the stage-1 time duration T_(s1). For example, attime t₁₃, the stage-timing signal generator 860 keeps the stage-timingsignal 862 at the logic high level. In another embodiment, the stage-2time duration T_(s2) ends at time t₁₄. For example, the signal 812changes from the logic high level to the logic low at time t₁₄, and inresponse, the stage-timing signal generator 860 changes the stage-timingsignal 862 from the logic high level to the logic low level at time t₁₄,indicating the end of the stage-2 time duration T_(s2).

In yet another embodiment, the stage-2 time duration T_(s2) is largerthan or equal to zero but smaller than or equal to T_(s2_max) inmagnitude, as shown by the waveform 720 of FIG. 7. For example, time t₁₄is larger than or equal to time t₁₃ in magnitude. In another example,time t₁₄ minus time t₁₃ is smaller than or equal to T_(s2_max) inmagnitude. In yet another embodiment, the stage-timing signal 862changes from the logic low level to the logic high level at time t₁₂,remains at the logic high level from time t₁₂ to time t₁₄, and changesfrom the logic high level back to the logic low level at time t₁₄. Forexample, time t₁₂ is no later than time t₁₄.

As shown in FIG. 9B, corresponding to each period (e.g., correspondingto each T_(M)) of the voltage 571, there are a stage-1 time duration(e.g., T_(s1)) and a stage-2 time duration (e.g., T_(s2)) according tocertain embodiments. In one embodiment, corresponding to one period ofthe voltage 571 (e.g., from time t₁₀ to time t₁₅), the stage-1 timeduration T_(s1) starts at time t₁₂ and ends at time t₁₃, and the stage-2time duration T_(s2) starts at time t₁₃ and ends at time t₁₄. In anotherembodiment, the stage-timing signal 862 changes from the logic low levelto the logic high level at time t₁₂, remains at the logic high levelfrom time t₁₂ to time t₁₄, and changes from the logic high level to thelogic low level at time t₁₄.

According to one embodiment, corresponding to one period of the voltage571 (e.g., from time t₁₀ to time t₁₅), the stage-1 time duration (e.g.,T_(s1) from time t₁₂ to time t₁₃) falls within the time duration whenthe TRIAC dimmer 510 is fired on (e.g., T_(dim_on) from time t₁₀ to timet₁₃), and the stage-2 time duration (e.g., T_(s2) from time t₁₃ to timet₁₄) falls within the time duration when the TRIAC dimmer 510 is notfired on (e.g., T_(dim_off) from time t₁₃ to time t₁₅). For example,corresponding to the period of the voltage 571 (e.g., from time t₁₀ totime t₁₅), during the stage-1 time duration (e.g., T_(s1)) and duringthe stage-2 time duration (e.g., T_(s2)), the sensing voltage 575 rampsup and down and the current 561 also ramps up and down. In anotherexample, corresponding to the period of the voltage 571 (e.g., from timet₁₀ to time t₁₅), outside the stage-1 time duration (e.g., T_(s1)) andthe stage-2 time duration (e.g., T_(s2)), the sensing voltage 575remains equal to zero. In yet another example, corresponding to theperiod of the voltage 571 (e.g., from time t₁₀ to time t₁₅), outside thestage-1 time duration (e.g., T_(s1)) and the stage-2 time duration(e.g., T_(s2)), the current 561 charges the capacitor 532.

Certain embodiments of the present invention provide stage-based dimmercontrol systems and methods with high compatibility, low costs, and/orhigh efficiency. For example, the stage-based dimmer control systems andmethods do not include a bleeder; hence the system layouts aresimplified with high compatibility achieved. In another example, thestage-based dimmer control systems and methods use one or more controlmechanisms in order to reduce bill of materials (BOM), raise energyefficiency, and lower system costs, while providing users withsatisfactory dimming effects for light emitting diodes. In yet anotherexample, the stage-based dimmer control systems and methods use astage-1 time duration (e.g., T_(s1)) and a stage-2 time duration (e.g.,T_(s2)), and each of these time durations is a function ofdimming-control phase angle ϕ_(dim_on) as shown in FIG. 7.

According to another embodiment, a system controller (e.g., themodulation controller 540) for a lighting system (e.g., the lightingsystem 500) includes a first controller terminal (e.g., the controllerterminal 542) configured to receive a first signal (e.g., the voltage571), and a second controller terminal (e.g., the controller terminal552) coupled to a first transistor terminal of a transistor (e.g., thegate terminal of the transistor 562). The transistor further includes asecond transistor terminal (e.g., the drain terminal of the transistor562) and a third transistor terminal (e.g., the source terminal of thetransistor 562). The second transistor terminal is coupled to a firstwinding terminal of a winding (e.g., the winding 560), and the winding(e.g., the winding 560) further includes a second winding terminalcoupled to a capacitor (e.g., the capacitor 530). Additionally, thesystem controller includes a third controller terminal (e.g., thecontroller terminal 554) coupled to the third transistor terminal of thetransistor (e.g., the source terminal of the transistor 562), and afourth controller terminal (e.g., the controller terminal 558) coupledto a resistor (e.g., the resistor 574) and configured to receive asecond signal (e.g., the sensing voltage 575). The second signalrepresents a magnitude of a current (e.g., the current 561) flowingthrough at least the winding (e.g., the winding 560), the thirdcontroller terminal (e.g., the controller terminal 554), the fourthcontroller terminal (e.g., the controller terminal 558), and theresistor (e.g., the resistor 574). The system controller (e.g., themodulation controller 540) is configured to: in response to the firstsignal (e.g., the voltage 571) becoming larger than a first threshold(e.g., the threshold voltage V_(th1_a)) in magnitude at a first time(e.g., the time t₂), cause the second signal (e.g., the sensing voltage575) to ramp up and down during a first duration of time (e.g., thestage-1 time duration T_(s1)); and in response to the first signal(e.g., the voltage 571) becoming smaller than a second threshold (e.g.,the threshold voltage V_(th1_b)) in magnitude at a third time (e.g., thetime t₄), cause the second signal (e.g., the sensing voltage 575) toramp up and down during a second duration of time (e.g., the stage-2time duration T_(s2)). The first duration of time (e.g., the stage-1time duration T_(s1)) starts at the first time (e.g., the time t₂) andends at a second time (e.g., the time t₃). The second duration of time(e.g., the stage-2 time duration T_(s2)) starts at the third time (e.g.,the time t₄) and ends at a fourth time (e.g., the time t₆). The systemcontroller (e.g., the modulation controller 540) is further configuredto cause the second signal (e.g., the sensing voltage 575) to remainequal to a constant magnitude from the second time (e.g., the time t₃)to the third time (e.g., the time t₄). The first time (e.g., the timet₂) is earlier than the second time (e.g., the time t₃), the second time(e.g., the time t₃) is earlier than the third time (e.g., the time t₄),and the third time (e.g., the time t₄) is earlier than the fourth time(e.g., the time t₆). For example, the system controller (e.g., themodulation controller 540) is implemented according to at least FIG. 5,FIG. 6A, and/or FIG. 9A.

In another example, the system controller (e.g., the modulationcontroller 540) is further configured to: in response to the firstsignal (e.g., the voltage 571) becoming smaller than the secondthreshold (e.g., the threshold voltage V_(th1_b)) in magnitude at aprevious time (e.g., the time t⁻¹) earlier than the first time (e.g.,the time t₂), determine the second time (e.g., the time t₃) to be apredetermined time duration (e.g., the predetermined time durationT_(P)) after the previous time (e.g., the time t⁻¹).

In yet another example, the fourth time (e.g., the time t₆) is a timewhen the capacitor (e.g., the capacitor 530) becomes completelydischarged. In yet another example, the first threshold (e.g., thethreshold voltage V_(th1_a)) and the second threshold (e.g., thethreshold voltage V_(th1_b)) are equal. In yet another example, thefirst threshold (e.g., the threshold voltage V_(th1_a)) and the secondthreshold (e.g., the threshold voltage V_(th1_b)) are not equal. In yetanother example, the constant magnitude is equal to zero. In yet anotherexample, each of the first controller terminal (e.g., the controllerterminal 542), the second controller terminal (e.g., the controllerterminal 552), the third controller terminal (e.g., the controllerterminal 554), and the fourth controller terminal (e.g., the controllerterminal 558) is a pin.

According to yet another embodiment, a system controller (e.g., themodulation controller 540) for a lighting system (e.g., the lightingsystem 500) includes a first controller terminal (e.g., the controllerterminal 542) configured to receive a first signal (e.g., the voltage571), and a second controller terminal (e.g., the controller terminal552) coupled to a first transistor terminal of a transistor (e.g., thegate terminal of the transistor 562). The transistor further includes asecond transistor terminal (e.g., the drain terminal of the transistor562) and a third transistor terminal (e.g., the source terminal of thetransistor 562), and the second transistor terminal is coupled to awinding (e.g., the winding 560). Additionally, the system controller(e.g., the modulation controller 540) further includes a thirdcontroller terminal (e.g., the controller terminal 554) coupled to thethird transistor terminal of the transistor (e.g., the source terminalof the transistor 562), and a fourth controller terminal (e.g., thecontroller terminal 558) coupled to a resistor (e.g., the resistor 574)and configured to receive a second signal (e.g., the sensing voltage575). The second signal represents a magnitude of a current (e.g., thecurrent 561) flowing through at least the winding (e.g., the winding560), the third controller terminal (e.g., the controller terminal 554),the fourth controller terminal (e.g., the controller terminal 558), andthe resistor (e.g., the resistor 574). The system controller (e.g., themodulation controller 540) is configured to: in response to the firstsignal (e.g., the voltage 571) becoming larger than a first threshold(e.g., the threshold voltage V_(th2_a)) in magnitude at a first time(e.g., the time t₁₁), cause the second signal (e.g., the sensing voltage575) to ramp up and down during a duration of time (e.g., the two-stagetotal time duration T_(st)). The duration of time (e.g., the two-stagetotal time duration T_(st)) starts at a second time (e.g., the time t₁₂)and ends at a third time (e.g., the time t₁₄). The third time (e.g., thetime t₁₄) is a time when the first signal (e.g., the voltage 571)becomes smaller than a second threshold (e.g., the threshold voltageV_(th2_b)) in magnitude. The system controller (e.g., the modulationcontroller 540) is further configured to cause the second signal (e.g.,the sensing voltage 575) to remain equal to a constant magnitude fromthe first time (e.g., the time t₁₁) to the second time (e.g., the timet₁₂). The first time (e.g., the time t₁₁) is earlier than the secondtime (e.g., the time t₁₂), and the second time (e.g., the time t₁₂) isearlier than the third time (e.g., the time t₁₄). For example, thesystem controller (e.g., the modulation controller 540) is implementedaccording to at least FIG. 5, FIG. 6B, and/or FIG. 9B.

In another example, the system controller (e.g., the modulationcontroller 540) is further configured to: in response to the firstsignal (e.g., the voltage 571) becoming larger than the first threshold(e.g., the threshold voltage V_(th2_a)) in magnitude at the first time(e.g., the time t₁₁), determine the second time (e.g., the time t₁₂) tobe a predetermined time duration (e.g., the predetermined time durationT_(Q)) after the first time (e.g., the time t₁₁). In yet anotherexample, the first threshold (e.g., the threshold voltage V_(th2_a)) andthe second threshold (e.g., the threshold voltage V_(th2_b)) are equal.In yet another example, the first threshold (e.g., the threshold voltageV_(th2_a)) and the second threshold (e.g., the threshold voltageV_(th2_b)) are not equal. In yet another example, the constant magnitudeis equal to zero. In yet another example, each of the first controllerterminal (e.g., the controller terminal 542), the second controllerterminal (e.g., the controller terminal 552), the third controllerterminal (e.g., the controller terminal 554), and the fourth controllerterminal (e.g., the controller terminal 558) is a pin.

According to yet another embodiment, a system controller (e.g., themodulation controller 540) for a lighting system (e.g., the lightingsystem 500) includes a first controller terminal (e.g., the controllerterminal 542) configured to receive a first signal (e.g., the voltage571). The first signal is related to a dimming-control phase angle(e.g., ϕ_(dim_on)). Additionally, the system controller (e.g., themodulation controller 540) includes a second controller terminal (e.g.,the controller terminal 552) coupled to a first transistor terminal of atransistor (e.g., the gate terminal of the transistor 562). Thetransistor further includes a second transistor terminal (e.g., thedrain terminal of the transistor 562) and a third transistor terminal(e.g., the source terminal of the transistor 562), and the secondtransistor terminal is coupled to a winding (e.g., the winding 560).Moreover, the system controller (e.g., the modulation controller 540)includes a third controller terminal (e.g., the controller terminal 554)coupled to the third transistor terminal of the transistor (e.g., thesource terminal of the transistor 562), and a fourth controller terminal(e.g., the controller terminal 558) coupled to a resistor (e.g., theresistor 574) and configured to receive a second signal (e.g., thesensing voltage 575). The second signal represents a magnitude of acurrent (e.g., the current 561) flowing through at least the winding(e.g., the winding 560), the third controller terminal (e.g., thecontroller terminal 554), the fourth controller terminal (e.g., thecontroller terminal 558), and the resistor (e.g., the resistor 574). Thesystem controller (e.g., the modulation controller 540) is configuredto, in response to the first signal (e.g., the voltage 571) satisfyingone or more predetermined conditions: cause the second signal (e.g., thesensing voltage 575) to ramp up and down during a first duration of time(e.g., the stage-1 time duration T_(s1)); and cause the second signal(e.g., the sensing voltage 575) to ramp up and down during a secondduration of time (e.g., the stage-2 time duration T_(s2)). The firstduration of time (e.g., the stage-1 time duration T_(s1)) starts at afirst time and ends at a second time, and the second time is the same asor later than the first time. The second duration of time (e.g., thestage-2 time duration T_(s2)) starts at a third time and ends at afourth time, and the fourth time is the same as or later than the thirdtime. The system controller (e.g., the modulation controller 540) isfurther configured to: in response to the dimming-control phase angle(e.g., ϕ_(dim_on)) increasing from a first angle magnitude (e.g., 0°) toa second angle magnitude (e.g., ϕ_(B)), keep the first duration of timeat a first predetermined constant; in response to the dimming-controlphase angle (e.g., ϕ_(dim_on)) increasing from the second anglemagnitude (e.g., ϕ_(B)) to a third angle magnitude (e.g., ϕ_(C)),increase the first duration of time; and in response to thedimming-control phase angle (e.g., ϕ_(dim_on)) increasing from the thirdangle magnitude (e.g., ϕ_(C)) to a fourth angle magnitude (e.g., 180°),keep the first duration of time at a second predetermined constant(e.g., T_(s1_max)). For example, the system controller (e.g., themodulation controller 540) is implemented according to at least FIG. 5,FIG. 6A, FIG. 6B, FIG. 7, FIG. 9A, and/or FIG. 9B.

In another example, the second time is earlier than the third time. Inyet another example, the second time is the same as the third time. Inyet another example, the first angle magnitude is equal to 0°, and thefourth angle magnitude is equal to 180°. In yet another example, thefirst predetermined constant is equal to zero. In yet another example,the system controller (e.g., the modulation controller 540) is furtherconfigured to, in response to the dimming-control phase angle (e.g.,ϕ_(dim_on)) increasing from the second angle magnitude (e.g., ϕ_(B)) tothe third angle magnitude (e.g., ϕ_(C)), increase the first duration oftime linearly with the increasing dimming-control phase angle at aconstant slope (e.g., the slope SL₁). In yet another example, the secondpredetermined constant (e.g., T_(s1_max)) is larger than zero.

According to yet another embodiment, a system controller (e.g., themodulation controller 540) for a lighting system (e.g., the lightingsystem 500) includes a first controller terminal (e.g., the controllerterminal 542) configured to receive a first signal (e.g., the voltage571). The first signal is related to a dimming-control phase angle(e.g., ϕ_(dim_on)). Additionally, the system controller (e.g., themodulation controller 540) includes a second controller terminal (e.g.,the controller terminal 552) coupled to a first transistor terminal of atransistor (e.g., the gate terminal of the transistor 562). Thetransistor further includes a second transistor terminal (e.g., thedrain terminal of the transistor 562) and a third transistor terminal(e.g., the source terminal of the transistor 562), and the secondtransistor terminal is coupled to a winding (e.g., the winding 560).Moreover, the system controller (e.g., the modulation controller 540)includes a third controller terminal (e.g., the controller terminal 554)coupled to the third transistor terminal of the transistor (e.g., thesource terminal of the transistor 562), and a fourth controller terminal(e.g., the controller terminal 558) coupled to a resistor (e.g., theresistor 574) and configured to receive a second signal (e.g., thesensing voltage 575). The second signal represents a magnitude of acurrent (e.g., the current 561) flowing through at least the winding(e.g., the winding 560), the third controller terminal (e.g., thecontroller terminal 554), the fourth controller terminal (e.g., thecontroller terminal 558), and the resistor (e.g., the resistor 574). Thesystem controller (e.g., the modulation controller 540) is configuredto, in response to the first signal (e.g., the voltage 571) satisfyingone or more predetermined conditions: cause the second signal (e.g., thesensing voltage 575) to ramp up and down during a first duration of time(e.g., the stage-1 time duration T_(s1)); and cause the second signal(e.g., the sensing voltage 575) to ramp up and down during a secondduration of time (e.g., the stage-2 time duration T_(s2)). The firstduration of time (e.g., the stage-1 time duration T_(s1)) starts at afirst time and ends at a second time, and the second time is the same asor later than the first time. The second duration of time (e.g., thestage-2 time duration T_(s2)) starts at a third time and ends at afourth time, and the fourth time is the same as or later than the thirdtime. The system controller (e.g., the modulation controller 540) isfurther configured to: in response to the dimming-control phase angle(e.g., ϕ_(dim_on)) increasing from a first angle magnitude (e.g., 0°) toa second angle magnitude (e.g., ϕ_(A)), keep the second duration of timeat a first predetermined constant; in response to the dimming-controlphase angle (e.g., ϕ_(dim_on)) increasing from the second anglemagnitude (e.g., ϕ_(A)) to a third angle magnitude (e.g., ϕ_(B)),increase the second duration of time; and in response to thedimming-control phase angle (e.g., ϕ_(dim_on)) increasing from the thirdangle magnitude (e.g., ϕ_(B)) to a fourth angle magnitude (e.g., 180°),keep the second duration of time at a second predetermined constant(e.g., T_(s2_max)). For example, the system controller (e.g., themodulation controller 540) is implemented according to at least FIG. 5,FIG. 6A, FIG. 6B, FIG. 7, FIG. 9A, and/or FIG. 9B.

In another example, the second time is earlier than the third time. Inyet another example, the second time is the same as the third time. Inyet another example, the first angle magnitude is equal to 0°, and thefourth angle magnitude is equal to 180°. In yet another example, thefirst predetermined constant is equal to zero. In yet another example,the system controller (e.g., the modulation controller 540) is furtherconfigured to, in response to the dimming-control phase angle (e.g.,ϕ_(dim_on)) increasing from the second angle magnitude (e.g., ϕ_(A)) tothe third angle magnitude (e.g., ϕ_(B)), increase the second duration oftime linearly with the increasing dimming-control phase angle at aconstant slope (e.g., the slope SL₂). In yet another example, the secondpredetermined constant (e.g., T_(s2_max)) is larger than zero.

According to yet another embodiment, a system controller (e.g., themodulation controller 540) for a lighting system (e.g., the lightingsystem 500) includes a first controller terminal (e.g., the controllerterminal 542) configured to receive a first signal (e.g., the voltage571). The first signal is related to a dimming-control phase angle(e.g., ϕ_(dim_on)). Additionally, the system controller (e.g., themodulation controller 540) includes a second controller terminal (e.g.,the controller terminal 552) coupled to a first transistor terminal of atransistor (e.g., the gate terminal of the transistor 562). Thetransistor further includes a second transistor terminal (e.g., thedrain terminal of the transistor 562) and a third transistor terminal(e.g., the source terminal of the transistor 562), and the secondtransistor terminal is coupled to a winding (e.g., the winding 560).Moreover, the system controller (e.g., the modulation controller 540)includes a third controller terminal (e.g., the controller terminal 554)coupled to the third transistor terminal of the transistor (e.g., thesource terminal of the transistor 562), and a fourth controller terminal(e.g., the controller terminal 558) coupled to a resistor (e.g., theresistor 574) and configured to receive a second signal (e.g., thesensing voltage 575). The second signal represents a magnitude of acurrent (e.g., the current 561) flowing through at least the winding(e.g., the winding 560), the third controller terminal (e.g., thecontroller terminal 554), the fourth controller terminal (e.g., thecontroller terminal 558), and the resistor (e.g., the resistor 574). Thesystem controller (e.g., the modulation controller 540) is configuredto, in response to the first signal (e.g., the voltage 571) satisfyingone or more predetermined conditions: cause the second signal (e.g., thesensing voltage 575) to ramp up and down during a first duration of time(e.g., the stage-1 time duration T_(s1)); and cause the second signal(e.g., the sensing voltage 575) to ramp up and down during a secondduration of time (e.g., the stage-2 time duration T_(s2)). The firstduration of time (e.g., the stage-1 time duration T_(s1)) starts at afirst time and ends at a second time, and the second time is the same asor later than the first time. The second duration of time (e.g., thestage-2 time duration T_(s2)) starts at a third time and ends at afourth time, and the fourth time is the same as or later than the thirdtime. The sum of the first duration of time (e.g., the stage-1 timeduration T_(s1)) and the second duration of time (e.g., the stage-2 timeduration T_(s2)) is equal to a total duration of time (e.g., thetwo-stage total time duration T_(st)). The system controller (e.g., themodulation controller 540) is further configured to: in response to thedimming-control phase angle (e.g., ϕ_(dim_on)) increasing from a firstangle magnitude (e.g., 0°) to a second angle magnitude (e.g., ϕ_(A)),keep the total duration of time at a first predetermined constant; inresponse to the dimming-control phase angle (e.g., ϕ_(dim_on))increasing from the second angle magnitude (e.g., ϕ_(A)) to a thirdangle magnitude (e.g., ϕ_(C)), increase the total duration of time; andin response to the dimming-control phase angle (e.g., ϕ_(dim_on))increasing from the third angle magnitude (e.g., ϕ_(C)) to a fourthangle magnitude (e.g., 180°), keep the total duration of time at asecond predetermined constant (e.g., T_(st) max). For example, thesystem controller (e.g., the modulation controller 540) is implementedaccording to at least FIG. 5, FIG. 6A, FIG. 6B, FIG. 7, FIG. 9A, and/orFIG. 9B.

In another example, the second time is earlier than the third time. Inyet another example, the second time is the same as the third time. Inyet another example, the first angle magnitude is equal to 0°, and thefourth angle magnitude is equal to 180°. In yet another example, thefirst predetermined constant is equal to zero. In yet another example,the second predetermined constant (e.g., T_(st_max)) is larger thanzero.

In yet another example, the system controller (e.g., the modulationcontroller 540) is further configured to, in response to thedimming-control phase angle (e.g., ϕ_(dim_on)) increasing from thesecond angle magnitude (e.g., ϕ_(A)) to the third angle magnitude (e.g.,ϕ_(C)): increase the total duration of time linearly at a first constantslope (e.g., the slope STL₁) in response to the dimming-control phaseangle increasing from the second angle magnitude (e.g., ϕ_(A)) to afourth angle magnitude (e.g., ϕ_(B)); and increase the total duration oftime linearly at a second constant slope (e.g., the slope STL₂) inresponse to the dimming-control phase angle increasing from the fourthangle magnitude (e.g., (B) to the third angle magnitude (e.g., ϕ_(C)).The fourth angle magnitude (e.g., ϕ_(B)) is larger than the second anglemagnitude (e.g., ϕ_(A)) and smaller than the third angle magnitude(e.g., ϕ_(C)). In yet another example, the first constant slope (e.g.,the slope STL₁) and the second constant slope (e.g., the slope STL₂) areequal. In yet another example, the first constant slope (e.g., the slopeSTL₁) and the second constant slope (e.g., the slope STL₂) are notequal.

In yet another example, the total duration of time is equal to the firstpredetermined constant in response to the dimming-control phase angle(e.g., ϕ_(dim_on)) being equal to the second angle magnitude (e.g.,ϕ_(A)); the total duration of time is equal to an intermediate magnitude(e.g., T_(st_mid)) in response to the dimming-control phase angle beingequal to the fourth angle magnitude (e.g., ϕ_(B)); and the totalduration of time is equal to the second predetermined constant inresponse to the dimming-control phase angle (e.g., ϕ_(dim_on)) beingequal to the third angle magnitude (e.g., ϕ_(C)). The intermediatemagnitude (e.g., T_(st_mid)) is larger than the first predeterminedconstant and smaller than the second predetermined constant.

According to yet another embodiment, a system controller (e.g., themodulation controller 540) for a lighting system (e.g., the lightingsystem 500) includes a first controller terminal (e.g., the controllerterminal 542) configured to receive a first signal (e.g., the voltage571), and a second controller terminal (e.g., the controller terminal552) coupled to a first transistor terminal of a transistor (e.g., thegate terminal of the transistor 562). The transistor further includes asecond transistor terminal (e.g., the drain terminal of the transistor562) and a third transistor terminal (e.g., the source terminal of thetransistor 562), and the second transistor terminal is coupled to afirst winding terminal of a winding (e.g., the winding 560). The winding(e.g., the winding 560) further includes a second winding terminalcoupled to a capacitor (e.g., the capacitor 530). Additionally, thesystem controller (e.g., the modulation controller 540) includes a thirdcontroller terminal (e.g., the controller terminal 554) coupled to thethird transistor terminal of the transistor (e.g., the source terminalof the transistor 562), and a fourth controller terminal (e.g., thecontroller terminal 558) coupled to a resistor (e.g., the resistor 574)and configured to receive a second signal (e.g., the sensing voltage575). The second signal represents a magnitude of a current (e.g., thecurrent 561) flowing through at least the winding (e.g., the winding560), the third controller terminal (e.g., the controller terminal 554),the fourth controller terminal (e.g., the controller terminal 558), andthe resistor (e.g., the resistor 574). The system controller (e.g., themodulation controller 540) is configured to determine whether or not aTRIAC dimmer is detected to be included in the lighting system and ifthe TRIAC dimmer is detected to be included in the lighting system,whether the TRIAC dimmer is a leading-edge TRIAC dimmer or atrailing-edge TRIAC dimmer. The system controller (e.g., the modulationcontroller 540) is further configured to, if the TRIAC dimmer isdetected to be included in the lighting system and the TRIAC dimmer isthe leading-edge TRIAC dimmer: in response to the first signal (e.g.,the voltage 571) becoming larger than a first threshold (e.g., thethreshold voltage V_(th_aa)) in magnitude at a first time (e.g., thetime t₂), cause the second signal (e.g., the sensing voltage 575) toramp up and down during a first duration of time (e.g., the stage-1 timeduration T_(s1)); and in response to the first signal (e.g., the voltage571) becoming smaller than a second threshold (e.g., the thresholdvoltage V_(th_bb)) in magnitude at a third time (e.g., the time t₄),cause the second signal (e.g., the sensing voltage 575) to ramp up anddown during a second duration of time (e.g., the stage-2 time durationT_(s2)). The first duration of time (e.g., the stage-1 time durationT_(s1)) starts at the first time (e.g., the time t₂) and ends at asecond time (e.g., the time t₃), and the second duration of time (e.g.,the stage-2 time duration T_(s2)) starts at the third time (e.g., thetime t₄) and ends at a fourth time (e.g., the time t₆). The systemcontroller (e.g., the modulation controller 540) is further configuredto, if the TRIAC dimmer is detected to be included in the lightingsystem and the TRIAC dimmer is the trailing-edge TRIAC dimmer: inresponse to the first signal (e.g., the voltage 571) becoming largerthan the first threshold (e.g., the threshold voltage V_(th_aa)) inmagnitude at a fifth time (e.g., the time t₁₁), cause the second signal(e.g., the sensing voltage 575) to ramp up and down during a duration oftime (e.g., the two-stage total time duration T_(st)). The duration oftime (e.g., the two-stage total time duration T_(st)) starts at a sixthtime (e.g., the time t₁₂) and ends at a seventh time (e.g., the timet₁₄). The seventh time (e.g., the time t₁₄) is a time when the firstsignal (e.g., the voltage 571) becomes smaller than the second threshold(e.g., the threshold voltage V_(th_bb)) in magnitude. For example, thesystem controller (e.g., the modulation controller 540) is implementedaccording to at least FIG. 5, FIG. 8, FIG. 9A, and/or FIG. 9B.

In another example, the system controller (e.g., the modulationcontroller 540) is further configured to, if the TRIAC dimmer isdetected to be included in the lighting system and the TRIAC dimmer isthe leading-edge TRIAC dimmer, cause the second signal (e.g., thesensing voltage 575) to remain equal to a constant magnitude from thesecond time (e.g., the time t₃) to the third time (e.g., the time t₄).In yet another example, the system controller (e.g., the modulationcontroller 540) is further configured to, if the TRIAC dimmer isdetected to be included in the lighting system and the TRIAC dimmer isthe trailing-edge TRIAC dimmer, cause the second signal (e.g., thesensing voltage 575) to remain equal to a constant magnitude from thefifth time (e.g., the time t₁₁) to the sixth time (e.g., the time t₁₂).

According to yet another embodiment, a method for a lighting system(e.g., the lighting system 500) includes receiving a first signal (e.g.,the voltage 571), and receiving a second signal (e.g., the sensingvoltage 575). The second signal represents a magnitude of a current(e.g., the current 561) flowing through at least a winding (e.g., thewinding 560). Additionally, the method includes: in response to thefirst signal (e.g., the voltage 571) becoming larger than a firstthreshold (e.g., the threshold voltage V_(th1_a)) in magnitude at afirst time (e.g., the time t₂), causing the second signal (e.g., thesensing voltage 575) to ramp up and down during a first duration of time(e.g., the stage-1 time duration T_(s1)); and in response to the firstsignal (e.g., the voltage 571) becoming smaller than a second threshold(e.g., the threshold voltage V_(th1_b)) in magnitude at a third time(e.g., the time t₄), causing the second signal (e.g., the sensingvoltage 575) to ramp up and down during a second duration of time (e.g.,the stage-2 time duration T_(s2)). The first duration of time (e.g., thestage-1 time duration T_(s1)) starts at the first time (e.g., the timet₂) and ends at a second time (e.g., the time t₃), and the secondduration of time (e.g., the stage-2 time duration T_(s2)) starts at thethird time (e.g., the time t₄) and ends at a fourth time (e.g., the timet₆). Moreover, the method includes causing the second signal (e.g., thesensing voltage 575) to remain equal to a constant magnitude from thesecond time (e.g., the time t₃) to the third time (e.g., the time t₄).The first time (e.g., the time t₂) is earlier than the second time(e.g., the time t₃), the second time (e.g., the time t₃) is earlier thanthe third time (e.g., the time t₄), and the third time (e.g., the timet₄) is earlier than the fourth time (e.g., the time t₆). For example,the method is implemented according to at least FIG. 5, FIG. 6A, and/orFIG. 9A.

In another example, the method further includes: in response to thefirst signal (e.g., the voltage 571) becoming smaller than the secondthreshold (e.g., the threshold voltage V_(th1_b)) in magnitude at aprevious time (e.g., the time t⁻¹) earlier than the first time (e.g.,the time t₂), determining the second time (e.g., the time t₃) to be apredetermined time duration (e.g., the predetermined time durationT_(P)) after the previous time (e.g., the time t⁻¹). In yet anotherexample, the constant magnitude is equal to zero.

According to yet another embodiment, a method for a lighting system(e.g., the lighting system 500) includes receiving a first signal (e.g.,the voltage 571) and receiving a second signal (e.g., the sensingvoltage 575). The second signal represents a magnitude of a current(e.g., the current 561) flowing through at least a winding (e.g., thewinding 560). Additionally, the method includes: in response to thefirst signal (e.g., the voltage 571) becoming larger than a firstthreshold (e.g., the threshold voltage V_(th2_a)) in magnitude at afirst time (e.g., the time t₁₁), causing the second signal (e.g., thesensing voltage 575) to ramp up and down during a duration of time(e.g., the two-stage total time duration T_(st)). The duration of time(e.g., the two-stage total time duration T_(st)) starts at a second time(e.g., the time t₁₂) and ends at a third time (e.g., the time t₁₄), andthe third time (e.g., the time t₁₄) is a time when the first signal(e.g., the voltage 571) becomes smaller than a second threshold (e.g.,the threshold voltage V_(th2_b)) in magnitude. Moreover, the methodincludes causing the second signal (e.g., the sensing voltage 575) toremain equal to a constant magnitude from the first time (e.g., the timet₁₁) to the second time (e.g., the time t₁₂). The first time (e.g., thetime t₁₁) is earlier than the second time (e.g., the time t₁₂), and thesecond time (e.g., the time t₁₂) is earlier than the third time (e.g.,the time t₁₄). For example, the method is implemented according to atleast FIG. 5, FIG. 6B, and/or FIG. 9B.

In another example, the method further includes: in response to thefirst signal (e.g., the voltage 571) becoming larger than the firstthreshold (e.g., the threshold voltage V_(th2_a)) in magnitude at thefirst time (e.g., the time t₁₁), determining the second time (e.g., thetime t₁₂) to be a predetermined time duration (e.g., the predeterminedtime duration T_(Q)) after the first time (e.g., the time t₁₁). In yetanother example, the constant magnitude is equal to zero.

According to yet another embodiment, a method for a lighting system(e.g., the lighting system 500) includes receiving a first signal (e.g.,the voltage 571). The first signal is related to a dimming-control phaseangle (e.g., ϕ_(dim_on)). Additionally, the method includes receiving asecond signal (e.g., the sensing voltage 575). The second signalrepresents a magnitude of a current (e.g., the current 561) flowingthrough at least a winding (e.g., the winding 560). Moreover, the methodincludes, in response to the first signal (e.g., the voltage 571)satisfying one or more predetermined conditions: causing the secondsignal (e.g., the sensing voltage 575) to ramp up and down during afirst duration of time (e.g., the stage-1 time duration T_(s1)); andcausing the second signal (e.g., the sensing voltage 575) to ramp up anddown during a second duration of time (e.g., the stage-2 time durationT_(s2)). The first duration of time (e.g., the stage-1 time durationT_(s1)) starts at a first time and ends at a second time, and the secondtime is the same as or later than the first time. The second duration oftime (e.g., the stage-2 time duration T_(s2)) starts at a third time andends at a fourth time, and the fourth time is the same as or later thanthe third time. The causing the second signal (e.g., the sensing voltage575) to ramp up and down during a first duration of time (e.g., thestage-1 time duration T_(s1)) includes: in response to thedimming-control phase angle (e.g., ϕ_(dim_on)) increasing from a firstangle magnitude (e.g., 0°) to a second angle magnitude (e.g., ϕ_(B)),keeping the first duration of time at a first predetermined constant; inresponse to the dimming-control phase angle (e.g., ϕ_(dim_on))increasing from the second angle magnitude (e.g., ϕ_(B)) to a thirdangle magnitude (e.g., ϕ_(C)), increasing the first duration of time;and in response to the dimming-control phase angle (e.g., ϕ_(dim_on))increasing from the third angle magnitude (e.g., ϕ_(C)) to a fourthangle magnitude (e.g., 180°), keeping the first duration of time at asecond predetermined constant (e.g., T_(s1_max)). For example, themethod is implemented according to at least FIG. 5, FIG. 6A, FIG. 6B,FIG. 7, FIG. 9A, and/or FIG. 9B.

In another example, the second time is earlier than the third time. Inyet another example, the second time is the same as the third time. Inyet another example, the first angle magnitude is equal to 0°, and thefourth angle magnitude is equal to 180°. In yet another example, thefirst predetermined constant is equal to zero. In yet another example,the process of, in response to the dimming-control phase angle (e.g.,ϕ_(dim_on)) increasing from the second angle magnitude (e.g., ϕ_(B)) toa third angle magnitude (e.g., ϕ_(C)), increasing the first duration oftime includes: in response to the dimming-control phase angle (e.g.,ϕ_(dim_on)) increasing from the second angle magnitude (e.g., ϕ_(B)) tothe third angle magnitude (e.g., ϕ_(C)), increasing the first durationof time linearly with the increasing dimming-control phase angle at aconstant slope (e.g., the slope SL₁). In yet another example, the secondpredetermined constant (e.g., T_(s1_max)) is larger than zero.

According to yet another embodiment, a method for a lighting system(e.g., the lighting system 500) includes receiving a first signal (e.g.,the voltage 571). The first signal is related to a dimming-control phaseangle (e.g., ϕ_(dim_on)). Additionally, the method includes receiving asecond signal (e.g., the sensing voltage 575). The second signalrepresents a magnitude of a current (e.g., the current 561) flowingthrough at least a winding (e.g., the winding 560). Moreover, the methodincludes, in response to the first signal (e.g., the voltage 571)satisfying one or more predetermined conditions: causing the secondsignal (e.g., the sensing voltage 575) to ramp up and down during afirst duration of time (e.g., the stage-1 time duration T_(s1)); andcausing the second signal (e.g., the sensing voltage 575) to ramp up anddown during a second duration of time (e.g., the stage-2 time durationT_(s2)). The first duration of time (e.g., the stage-1 time durationT_(s1)) starts at a first time and ends at a second time, and the secondtime is the same as or later than the first time. The second duration oftime (e.g., the stage-2 time duration T_(s2)) starts at a third time andends at a fourth time, and the fourth time is the same as or later thanthe third time. The causing the second signal (e.g., the sensing voltage575) to ramp up and down during a second duration of time (e.g., thestage-2 time duration T_(s2)) includes: in response to thedimming-control phase angle (e.g., ϕ_(dim_on)) increasing from a firstangle magnitude (e.g., 0°) to a second angle magnitude (e.g., ϕ_(A)),keeping the second duration of time at a first predetermined constant;in response to the dimming-control phase angle (e.g., ϕ_(dim_on))increasing from the second angle magnitude (e.g., ϕ_(A)) to a thirdangle magnitude (e.g., ϕ_(B)), increasing the second duration of time;and in response to the dimming-control phase angle (e.g., ϕ_(dim_on))increasing from the third angle magnitude (e.g., ϕ_(B)) to a fourthangle magnitude (e.g., 180°), keeping the second duration of time at asecond predetermined constant (e.g., T_(s2_max)). For example, themethod is implemented according to at least FIG. 5, FIG. 6A, FIG. 6B,FIG. 7, FIG. 9A, and/or FIG. 9B.

In another example, the second time is earlier than the third time. Inyet another example, the second time is the same as the third time. Inyet another example, the first angle magnitude is equal to 0°, and thefourth angle magnitude is equal to 180°. In yet another example, thefirst predetermined constant is equal to zero. In yet another example,the process of, in response to the dimming-control phase angle (e.g.,ϕ_(dim_on)) increasing from the second angle magnitude (e.g., ϕ_(A)) toa third angle magnitude (e.g., ϕ_(B)), increasing the second duration oftime includes: in response to the dimming-control phase angle (e.g.,ϕ_(dim_on)) increasing from the second angle magnitude (e.g., ϕ_(A)) tothe third angle magnitude (e.g., ϕ_(B)), increasing the second durationof time linearly with the increasing dimming-control phase angle at aconstant slope (e.g., the slope SL₂). In yet another example, the secondpredetermined constant (e.g., T_(s2_max)) is larger than zero.

According to yet another embodiment, a method for a lighting system(e.g., the lighting system 500) includes receiving a first signal (e.g.,the voltage 571). The first signal is related to a dimming-control phaseangle (e.g., ϕ_(dim_on)). Additionally, the method includes receiving asecond signal (e.g., the sensing voltage 575). The second signalrepresents a magnitude of a current (e.g., the current 561) flowingthrough at least a winding (e.g., the winding 560). Moreover, the methodincludes, in response to the first signal (e.g., the voltage 571)satisfying one or more predetermined conditions: causing the secondsignal (e.g., the sensing voltage 575) to ramp up and down during afirst duration of time (e.g., the stage-1 time duration T_(s1)); andcausing the second signal (e.g., the sensing voltage 575) to ramp up anddown during a second duration of time (e.g., the stage-2 time durationT_(s2)). The first duration of time (e.g., the stage-1 time durationT_(s1)) starts at a first time and ends at a second time, and the secondtime is the same as or later than the first time. The second duration oftime (e.g., the stage-2 time duration T_(s2)) starts at a third time andends at a fourth time, and the fourth time is the same as or later thanthe third time. A sum of the first duration of time (e.g., the stage-1time duration T_(s1)) and the second duration of time (e.g., the stage-2time duration T_(s2)) is equal to a total duration of time (e.g., thetwo-stage total time duration T_(st)). The causing the second signal(e.g., the sensing voltage 575) to ramp up and down during a firstduration of time (e.g., the stage-1 time duration T_(s1)) and thecausing the second signal (e.g., the sensing voltage 575) to ramp up anddown during a second duration of time (e.g., the stage-2 time durationT_(s2)) include: in response to the dimming-control phase angle (e.g.,ϕ_(dim_on)) increasing from a first angle magnitude (e.g., 0°) to asecond angle magnitude (e.g., GA), keeping the total duration of time ata first predetermined constant; in response to the dimming-control phaseangle (e.g., ϕ_(dim_on)) increasing from the second angle magnitude(e.g., ϕ_(A)) to a third angle magnitude (e.g., ϕ_(C)), increasing thetotal duration of time; and in response to the dimming-control phaseangle (e.g., ϕ_(dim_on)) increasing from the third angle magnitude(e.g., ϕ_(C)) to a fourth angle magnitude (e.g., 180°), keeping thetotal duration of time at a second predetermined constant (e.g.,T_(st_max)). For example, the method is implemented according to atleast FIG. 5, FIG. 6A, FIG. 6B, FIG. 7, FIG. 9A, and/or FIG. 9B.

In another example, the second time is earlier than the third time. Inyet another example, the second time is the same as the third time. Inyet another example, the first angle magnitude is equal to 0°, and thefourth angle magnitude is equal to 180°. In yet another example, thefirst predetermined constant is equal to zero. In yet another example,the second predetermined constant (e.g., T_(st_max)) is larger thanzero.

In yet another example, the process of, in response to thedimming-control phase angle (e.g., ϕ_(dim_on)) increasing from thesecond angle magnitude (e.g., ϕ_(A)) to a third angle magnitude (e.g.,ϕ_(C)), increasing the total duration of time includes: increasing thetotal duration of time linearly at a first constant slope (e.g., theslope STL₁) in response to the dimming-control phase angle increasingfrom the second angle magnitude (e.g., ϕ_(A)) to a fourth anglemagnitude (e.g., ϕ_(B)); and increasing the total duration of timelinearly at a second constant slope (e.g., the slope STL₂) in responseto the dimming-control phase angle increasing from the fourth anglemagnitude (e.g., ϕ_(B)) to the third angle magnitude (e.g., ϕ_(C)). Thefourth angle magnitude (e.g., ϕ_(B)) is larger than the second anglemagnitude (e.g., ϕ_(A)) and smaller than the third angle magnitude(e.g., ϕ_(C)). In yet another example, the first constant slope (e.g.,the slope STL₁) and the second constant slope (e.g., the slope STL₂) areequal. In yet another example, the first constant slope (e.g., the slopeSTL₁) and the second constant slope (e.g., the slope STL₂) are notequal. In yet another example, the total duration of time is equal tothe first predetermined constant in response to the dimming-controlphase angle (e.g., ϕ_(dim_on)) being equal to the second angle magnitude(e.g., ϕ_(A)), the total duration of time is equal to an intermediatemagnitude (e.g., T_(st_mid)) in response to the dimming-control phaseangle being equal to the fourth angle magnitude (e.g., ϕ_(B)), and thetotal duration of time is equal to the second predetermined constant inresponse to the dimming-control phase angle (e.g., ϕ_(dim_on)) beingequal to the third angle magnitude (e.g., ϕ_(C)). The intermediatemagnitude (e.g., T_(st_mid)) is larger than the first predeterminedconstant and smaller than the second predetermined constant.

According to yet another embodiment, a method for a lighting system(e.g., the lighting system 500) includes receiving a first signal (e.g.,the voltage 571) and receiving a second signal (e.g., the sensingvoltage 575). The second signal represents a magnitude of a current(e.g., the current 561) flowing through at least a winding (e.g., thewinding 560). Additionally, the method includes determining whether ornot a TRIAC dimmer is detected to be included in the lighting system andif the TRIAC dimmer is detected to be included in the lighting system,whether the TRIAC dimmer is a leading-edge TRIAC dimmer or atrailing-edge TRIAC dimmer. Moreover, the method includes, if the TRIACdimmer is detected to be included in the lighting system and the TRIACdimmer is the leading-edge TRIAC dimmer: in response to the first signal(e.g., the voltage 571) becoming larger than a first threshold (e.g.,the threshold voltage V_(th_aa)) in magnitude at a first time (e.g., thetime t₂), causing the second signal (e.g., the sensing voltage 575) toramp up and down during a first duration of time (e.g., the stage-1 timeduration T_(s1)); and in response to the first signal (e.g., the voltage571) becoming smaller than a second threshold (e.g., the thresholdvoltage V_(th_bb)) in magnitude at a third time (e.g., the time t₄),causing the second signal (e.g., the sensing voltage 575) to ramp up anddown during a second duration of time (e.g., the stage-2 time durationT_(s2)). The first duration of time (e.g., the stage-1 time durationT_(s1)) starts at the first time (e.g., the time t₂) and ends at asecond time (e.g., the time t₃), and the second duration of time (e.g.,the stage-2 time duration T_(s2)) starts at the third time (e.g., thetime t₄) and ends at a fourth time (e.g., the time t₆). Also, the methodincludes, if the TRIAC dimmer is detected to be included in the lightingsystem and the TRIAC dimmer is the trailing-edge TRIAC dimmer: inresponse to the first signal (e.g., the voltage 571) becoming largerthan the first threshold (e.g., the threshold voltage V_(th_aa)) inmagnitude at a fifth time (e.g., the time t₁₁), causing the secondsignal (e.g., the sensing voltage 575) to ramp up and down during aduration of time (e.g., the two-stage total time duration T_(st)). Theduration of time (e.g., the two-stage total time duration T_(st)) startsat a sixth time (e.g., the time t₁₂) and ends at a seventh time (e.g.,the time t₁₄). The seventh time (e.g., the time t₁₄) is a time when thefirst signal (e.g., the voltage 571) becomes smaller than the secondthreshold (e.g., the threshold voltage V_(th_bb)) in magnitude. Forexample, the method is implemented according to at least FIG. 5, FIG. 8,FIG. 9A, and/or FIG. 9B.

In another example, the method further includes: if the TRIAC dimmer isdetected to be included in the lighting system and the TRIAC dimmer isthe leading-edge TRIAC dimmer, causing the second signal (e.g., thesensing voltage 575) to remain equal to a constant magnitude from thesecond time (e.g., the time t₃) to the third time (e.g., the time t₄).In yet another example, the method further includes: if the TRIAC dimmeris detected to be included in the lighting system and the TRIAC dimmeris the trailing-edge TRIAC dimmer, causing the second signal (e.g., thesensing voltage 575) to remain equal to a constant magnitude from thefifth time (e.g., the time t₁₁) to the sixth time (e.g., the time t₁₂).

For example, some or all components of various embodiments of thepresent invention each are, individually and/or in combination with atleast another component, implemented using one or more softwarecomponents, one or more hardware components, and/or one or morecombinations of software and hardware components. In another example,some or all components of various embodiments of the present inventioneach are, individually and/or in combination with at least anothercomponent, implemented in one or more circuits, such as one or moreanalog circuits and/or one or more digital circuits. In yet anotherexample, various embodiments and/or examples of the present inventioncan be combined.

Although specific embodiments of the present invention have beendescribed, it will be understood by those of skill in the art that thereare other embodiments that are equivalent to the described embodiments.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

What is claimed is:
 1. A system controller for a lighting system, thesystem controller comprising: a first controller terminal configured toreceive a first signal; and a second controller terminal coupled to aresistor and configured to receive a second signal, the second signalrepresenting a magnitude of a current flowing through at least theresistor; wherein the system controller is configured to: in response tothe first signal becoming larger than a first threshold in magnitude ata first time, cause the second signal to ramp up and down during a firstduration of time, the first duration of time starting at the first timeand ending at a second time; and in response to the first signalbecoming smaller than a second threshold in magnitude at a third time,cause the second signal to ramp up and down during a second duration oftime, the second duration of time starting at the third time and endingat a fourth time; wherein the system controller is further configured tocause the second signal to remain equal to a constant magnitude from thesecond time to the third time; wherein: the first time is earlier thanthe second time; the second time is earlier than the third time; and thethird time is earlier than the fourth time.
 2. The system controller ofclaim 1 is further configured to: in response to the first signalbecoming smaller than the second threshold in magnitude at a previoustime earlier than the first time, determine the second time to be apredetermined time duration after the previous time.
 3. The systemcontroller of claim 1 wherein the fourth time is a time when a capacitorcoupled to the system controller becomes completely discharged.
 4. Thesystem controller of claim 1 wherein the first threshold and the secondthreshold are equal.
 5. The system controller of claim 1 wherein thefirst threshold and the second threshold are not equal.
 6. The systemcontroller of claim 1 wherein the constant magnitude is equal to zero.7. The system controller of claim 1 wherein each of the first controllerterminal and the second controller terminal is a pin.
 8. A systemcontroller for a lighting system, the system controller comprising: afirst controller terminal configured to receive a first signal; and asecond controller terminal coupled to a resistor and configured toreceive a second signal, the second signal representing a magnitude of acurrent flowing through at least the resistor; wherein the systemcontroller is configured to: in response to the first signal becominglarger than a first threshold in magnitude at a first time, cause thesecond signal to ramp up and down during a duration of time, theduration of time starting at a second time and ending at a third time,the third time being a time when the first signal becomes smaller than asecond threshold in magnitude; wherein the system controller is furtherconfigured to cause the second signal to remain equal to a constantmagnitude from the first time to the second time; wherein: the firsttime is earlier than the second time; and the second time is earlierthan the third time.
 9. The system controller of claim 8 is furtherconfigured to: in response to the first signal becoming larger than thefirst threshold in magnitude at the first time, determine the secondtime to be a predetermined time duration after the first time.
 10. Thesystem controller of claim 8 wherein the first threshold and the secondthreshold are equal.
 11. The system controller of claim 8 wherein thefirst threshold and the second threshold are not equal.
 12. The systemcontroller of claim 8 wherein the constant magnitude is equal to zero.13. The system controller of claim 8 wherein each of the firstcontroller terminal and the second controller terminal is a pin.
 14. Asystem controller for a lighting system, the system controllercomprising: a first controller terminal configured to receive a firstsignal; and a second controller terminal coupled to a resistor andconfigured to receive a second signal, the second signal representing amagnitude of a current flowing through at least the resistor; whereinthe system controller is configured to determine whether or not a TRIACdimmer is detected to be included in the lighting system and if theTRIAC dimmer is detected to be included in the lighting system, whetherthe TRIAC dimmer is a leading-edge TRIAC dimmer or a trailing-edge TRIACdimmer; wherein the system controller is further configured to, if theTRIAC dimmer is detected to be included in the lighting system and theTRIAC dimmer is the leading-edge TRIAC dimmer: in response to the firstsignal becoming larger than a first threshold in magnitude at a firsttime, cause the second signal to ramp up and down during a firstduration of time, the first duration of time starting at the first timeand ending at a second time; and in response to the first signalbecoming smaller than a second threshold in magnitude at a third time,cause the second signal to ramp up and down during a second duration oftime, the second duration of time starting at the third time and endingat a fourth time.
 15. The system controller of claim 14 wherein thesystem controller is further configured to, if the TRIAC dimmer isdetected to be included in the lighting system and the TRIAC dimmer isthe trailing-edge TRIAC dimmer: in response to the first signal becominglarger than the first threshold in magnitude at a fifth time, cause thesecond signal to ramp up and down during a duration of time, theduration of time starting at a sixth time and ending at a seventh time,the seventh time being a time when the first signal becomes smaller thanthe second threshold in magnitude.
 16. The system controller of claim 15is further configured to, if the TRIAC dimmer is detected to be includedin the lighting system and the TRIAC dimmer is the trailing-edge TRIACdimmer, cause the second signal to remain equal to a constant magnitudefrom the fifth time to the sixth time.
 17. The system controller ofclaim 14 is further configured to, if the TRIAC dimmer is detected to beincluded in the lighting system and the TRIAC dimmer is the leading-edgeTRIAC dimmer, cause the second signal to remain equal to a constantmagnitude from the second time to the third time.
 18. A method for alighting system, the method comprising: receiving a first signal;receiving a second signal, the second signal representing a magnitude ofa current flowing through at least a winding; determining whether or nota TRIAC dimmer is detected to be included in the lighting system and ifthe TRIAC dimmer is detected to be included in the lighting system,whether the TRIAC dimmer is a leading-edge TRIAC dimmer or atrailing-edge TRIAC dimmer; and if the TRIAC dimmer is detected to beincluded in the lighting system and the TRIAC dimmer is the leading-edgeTRIAC dimmer, in response to the first signal becoming larger than afirst threshold in magnitude at a first time, causing the second signalto ramp up and down during a first duration of time, the first durationof time starting at the first time and ending at a second time; and inresponse to the first signal becoming smaller than a second threshold inmagnitude at a third time, causing the second signal to ramp up and downduring a second duration of time, the second duration of time startingat the third time and ending at a fourth time.
 19. The method of claim18 and further comprising: if the TRIAC dimmer is detected to beincluded in the lighting system and the TRIAC dimmer is the leading-edgeTRIAC dimmer, causing the second signal to remain equal to a constantmagnitude from the second time to the third time.
 20. A method for alighting system, the method comprising: receiving a first signal;receiving a second signal, the second signal representing a magnitude ofa current flowing through at least a winding; determining whether or nota TRIAC dimmer is detected to be included in the lighting system and ifthe TRIAC dimmer is detected to be included in the lighting system,whether the TRIAC dimmer is a leading-edge TRIAC dimmer or atrailing-edge TRIAC dimmer; and if the TRIAC dimmer is detected to beincluded in the lighting system and the TRIAC dimmer is thetrailing-edge TRIAC dimmer, in response to the first signal becominglarger than a first threshold in magnitude at a first time, causing thesecond signal to ramp up and down during a duration of time, theduration of time starting at a second time and ending at a third time,the third time being a time when the first signal becomes smaller thanthe second threshold in magnitude.
 21. The method of claim 20, furthercomprising: if the TRIAC dimmer is detected to be included in thelighting system and the TRIAC dimmer is the trailing-edge TRIAC dimmer,causing the second signal to remain equal to a constant magnitude fromthe first time to the second time.